WO2014105685A1

WO2014105685A1 - Method for preparing aliphatic polyesters from diols

Info

Publication number: WO2014105685A1
Application number: PCT/US2013/076863
Authority: WO
Inventors: Gang ZUO; Qiongdan XIE; Tian TANG; Qiuju Wu
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2012-12-25
Filing date: 2013-12-20
Publication date: 2014-07-03
Also published as: CN103897157B; CN103897157A

Abstract

Disclosed is a method for preparing an aliphatic polyester by heating a mixture of a diol, a ruthenium catalyst and optionally a solvent or a solvent system. According to the method of the invention, the method is conducted at a temperature ranging from 100-300°C for 1-60 hours to provide the aliphatic polyesters with high yield.

Description

TITLE

METHOD FOR PREPARING ALIPHATIC POLYESTERS FROM DIOLS

FIELD OF THE INVENTION

This invention relates to a method for preparing aliphatic polyesters directly from diols in the presence of a ruthenium catalyst.

BACKGROUND OF THE INVENTION

Polyester is conventionally prepared from a condensation reaction of a diacid and a diol.

The commercial synthesis of polyesters typically involves two steps: (1) condensation/transesterification: reacting a diacid or its ester and a diol in excess amount to form oligomers at a relative lower temperature while continuously removal of small volatile molecules, such as H₂0, ethanol or methanol; (2) polymerization: heating the oligomers to certain high temperature (e.g., 250°C for polyethylene terephthalate) under reduced pressure to remove one excess monomer which is more volatile, usually the diol, to achieve high molecular weight polyesters. The major drawback of the condensation polymerization method is the need of removal of the excess monomer at high vacuum and high temperature, which adds to the energy cost and subjects the polyester product to potential degradation.

Alternatively, polyester can also be produced by ring-opening polymerization of a lactone. For example, polycaprolactone is commercially produced by ring-opening polymerization of a caprolactone, which is a cyclic ester monomer. Ester co-polymers can also be prepared by ring opening of the mixture of cyclic ester monomers, see J. Am. Chem.

Soc. 2010, 132, 1750-1751 disclosed by N. Nomura et al.

Recently, Milstein et al. (Science 2007, 317, 790) discloses that by treating various alcohols with a Ru catalyst can produce various esters and release H₂ as the only byproduct.

The novel "dehydrogenative esterification" method offers several advantages such as high yield and high turnover number as well as minimum byproduct generation, thus environmental friendly.

Polyesters can be divided into 3 categories including aliphatic, semi-aromatic, and aromatic based on the monomer(s) used. In describing polyesters, polyesters are usually described based on the monomer(s) used. For example, polyglycolide or polyglycolic acid (PGA), an aliphatic polyester, is prepared from the condensation of gly colic acid; polyethylene terephthalate (PET), a semi-aromatic polyester, is prepared from polycondensation of terephthalic acid with ethylene glycol.

Given the biodegradable nature of the aliphatic polyesters such as PGA, this class of polyesters attract more attentions recently. Consequently, any improvements made in their manufacturing processes are welcomed. The applicant of this invention discovered that aliphatic polyesters could be produced from various diols by a similar dehydrogenative polymerization method. The polymerization can be carried out in the presence of solvents or in a solventless condition.

SUMMARY OF THE INVENTION

This invention provides a method for preparing polyesters of Formula 1

comprising:

(a) combining a diol of Formula 2, a ruthenium catalyst of Formula 3

3

and optionally a solvent or a solvent system to form a reaction mixture,

wherein

A is -(CH₂)p-Wq- (CH₂)_r -, where W is selected from the group consisting of C₃-C₁₀ cycloalkyl, p is an integer of from 1 to 8, q is 0 or 1, r is an integer of from 1 to 8, and when q is 0, then the sum of p and r is an integer of from 3 to 14; the sum of k and n is an integer of from 10 to 150;

Li and L₂ are each independently selected from the group consisting of P(R¹)₂,

P(OR2)₂, N(R3)₂;

L₃ is a mono-dentate two-electron donor selected from the group consisting of CO,

P(R!)₃, P(0R2)₃, NO⁺, nitrile (R⁴CN) and isonitrile (R⁵NC);

R¹ , R², R³, R⁴ and R⁵ are each independently selected from the group consisting of alkyl, cycloalkyl, aryl, alkylaryl, heterocyclyl and heteroaryl;

and

(b) heating the reaction mixture at a temperature in the range of 100-300°C for 1-60 hours to form the polyesters of Formula 1.

The present methods are described below in further detail. In the following schemes the definitions of are as defined above unless otherwise stated. DETAILS OF THE INVENTION

All publications, patent applications, patents and other references mentioned herein, if not otherwise indicated, are explicitly incorporated by reference herein in their entirety for all purposes as if fully set forth.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

As used herein, the term "produced from" is synonymous to "comprising". As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains" or "containing," or any other variation thereof, are intended to cover a nonexclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The transitional phrase "consisting of excludes any element, step, or ingredient not specified. If in the claim, such a phrase would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase "consisting of appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

The transitional phrase "consisting essentially of is used to define a composition, method or apparatus that includes materials, steps, features, components, or elements, in addition to those literally discussed, provided that these additional materials, steps features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term "consisting essentially of occupies a middle ground between "comprising" and "consisting of.

The term "comprising" is intended to include embodiments encompassed by the terms "consisting essentially of and "consisting of . Similarly, the term "consisting essentially of is intended to include embodiments encompassed by the term "consisting of .

In the above recitations, the total number of carbon atoms in a substituent group is indicated by the "Cj-Cj" prefix where i and j are numbers from 1 to 16.

The term "alkyl", used alone or as part of another group, refers, in one embodiment, to a "Ci to C₁₆ alkyl" and denotes linear and branched, saturated or unsaturated (e.g., alkenyl, alkynyl) groups, the latter only when the number of carbon atoms in the alkyl chain is greater than or equal to two, and can contain mixed structures. Preferred are alkyl groups containing from 1 to 12 carbon atoms (C^ to C^ alkyls). More preferred are alkyl groups containing from 1 to 10 carbon atoms (C^ to C^Q alkyls). Examples of saturated alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec- butyl, tert-butyl, amyl, tert-amyl, and hexyl. Examples of alkenyl groups include, but are not limited to, vinyl, allyl, butenyl and the like. Examples of alkynyl groups include, but are not limited to, ethynyl, propynyl and the like. Similarly, the term "C to C12 alkylene" denotes a bivalent radicals of 1 to 12 carbons.

The alkyl group can be unsubstituted, or substituted with one or more substituents selected from the group consisting of halogen, hydroxy, alkoxy, aryloxy, alkylaryloxy, heteroaryloxy, oxo, cycloalkyl, phenyl, heteroaryls, heterocyclyl, naphthyl, amino, alkylamino, arylamino, heteroarylamino, dialkylamino, diarylamino, alkylarylamino, alkylheteroarylamino, arylheteroarylamino, acyl, acyloxy, nitro, carboxy, carbamoyl, carboxamide, cyano, sulfonyl, sulfonylamino, sulfmyl, sulfinylamino, thiol, alkylthio, arylthio, or alkylsulfonyl groups. Any substituents can be unsubstituted or further substituted with any one of these aforementioned substituents. By way of illustration, an "alkoxyalkyl" is an alkyl that is substituted with an alkoxy group.

The term "cycloalkyl" used herein alone or as part of another group, refers to a "C3 to C Q cycloalkyl" and denotes any unsaturated or unsaturated (e.g., cycloalkenyl, cycloalkynyl) monocyclic or polycyclic group. Nonlimiting examples of cycloalkyl groups are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.2]octyl, or adamantyl. Examples or cycloalkenyl groups include cyclopentenyl, cyclohexenyl and the like. The cycloalkyl group can be unsubstituted or substituted with any one or more of the substituents defined above for alkyl. Similarly, the term "cycloalkylene" means a bivalent cycloalkyl, as defined above, where the cycloalkyl radical is bonded at two positions connecting together two separate additional groups.

The term "aryl" used herein alone or as part of another group denotes an aromatic ring system containing from 6-14 ring carbon atoms. The aryl ring can be a monocyclic, bicyclic, tricyclic and the like. Non-limiting examples of aryl groups are phenyl, naphthyl including 1 -naphthyl and 2-naphthyl, and the like. The aryl group can be unsubstituted or substituted through available carbon atoms with one or more groups defined hereinabove for alkyl. An arylalkyl group denotes an aryl group bonded to an alkyl group (e.g., benzyl).

The term "heteroaryl" used herein alone or as part of another group denotes a heteroaromatic system containing at least one heteroatom ring atom selected from nitrogen, sulfur and oxygen. The heteroaryl contains 5 or more ring atoms. The heteroaryl group can be monocyclic, bicyclic, tricyclic and the like. Also included in this expression are the benzoheterocyclic rings. If nitrogen is a ring atom, the present invention also contemplates the N-oxides of the nitrogen containing heteroaryls. Nonlimiting examples of heteroaryls include thienyl, benzothienyl, 1-naphthothienyl, thianthrenyl, furyl, benzofuryl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolyl, isoindolyl, indazolyl, purinyl, isoquinolyl, quinolyl, naphthyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, carbolinyl, thiazolyl, oxazolyl, isothiazolyl, isoxazolyl and the like. The heteroaryl group can be unsubstituted or substituted through available atoms with one or more groups defined hereinabove for alkyl.

The term "heterocyclic ring" or "heterocyclyl" used herein alone or as part of another group denotes a three-membered to eight-membered rings that have 1 to 4 heteroatoms, such as oxygen, sulfur and/or nitrogen. These three-membered to eight-membered rings can be saturated, fully unsaturated or partially unsaturated. Non-limiting examples of heterocyclic rings include oxiranyl, oxetanyl, piperidinyl, piperidinyl, pyrrolidinyl pyrrolinyl, pyrazolinyl, pyrazolidinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyranyl, thiopyranyl, piperazinyl, indolinyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothiophenyl, tetrahydrothiophenyl, dihydropyranyl, tetrahydropyranyl, and the like. The heterocyclyl group can be unsubstituted or substituted through available atoms with one or more groups defined hereinabove for alkyl.

When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is recited, the recited range should be construed as including ranges " 1 to 4", " 1 to 3", " 1-2", "1-2 & 4-5", "1-3 & 5", and the like. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range.

When the term "about" is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to.

Further, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, a condition A "or" B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the indefinite articles "a" and "an" preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore "a" or "an" should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

"mol%" or "mole%" refers to mole percent.

In describing and/or claiming this invention, the term "homopolymer" refers to a polymer derived from polymerization of one species of repeating unit. The term 'copolymer" refers to polymers comprising copolymerized units resulting from copolymerization of two or more comonomers. "Dipolymer" refers to polymers consisting essentially of two comonomer-derived units and "terpolymer" means a copolymer consisting essentially of three comonomer-derived units. For example, the polyester of Formula 1 consists two repeating units, thus can be either considered to be a copolymer or a dipolymer.

Embodiments of the present invention include:

Embodiment 1. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein Lj is P(R¹)2- Embodiment 2. The method of Embodiment 1 wherein R¹ is t-butyl.

Embodiment 3. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein L₂ is N(R³)2- Embodiment 4. The method of Embodiment 3 wherein R³ is ethyl.

Embodiment 5. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein L₃ is CO.

Embodiment 6. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein the amount of the ruthenium catalyst of Formula 3 ranges from about 0.05 mol% to about 5 mol% per mole of the diol of Formula

2.

Embodiment 7. The method of Embodiment 6 wherein the amount of the ruthenium catalyst of Formula 3 ranges from about 0.1 mol% to about 1 mol% per mole of the diol of Formula 2.

Embodiment 8. The method of Embodiment 7 wherein the amount of the ruthenium catalyst of Formula 3 ranges from about 0.2 mol% to about 0.8 mol% per mole of the diol of Formula 2.

Embodiment 9. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein the solvent or the solvent system is selected from the group consisting of cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, anisole, mesitylene, tetrahydrofuran, 1 ,2-dimethoxyethane, 1,4-dioxane, diglyme, dimethylformamide, dimethylsulfoxide, and mixtures thereof.

Embodiment 10. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein the amount of the solvent or the solvent system is in the range of from about 0.01 L to about 0.45 L per mole of the diol of Formula 2.

Embodiment 11. The method of Embodiment 10 wherein the amount of the solvent or the solvent system is in the range of from about 0.1 L to about 0.4 L per mole of the diol of Formula 2.

Embodiment 12. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein the polyester of Formula 1 is formed in an inert gas atmosphere. Embodiment 13. The method of Embodiment 12 wherein the polyester of Formula 1 is formed at a pressure from about 1 bar to about 10 bar.

Embodiment 14. The method of Embodiment 13 wherein the polyester of Formula 1 is formed at a pressure from about 1 bar to about 5 bar.

Embodiment 15. The method of Embodiment 14 wherein the polyester of Formula 1 is formed at a pressure near the normal atmospheric pressure.

Embodiment 16. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein the heating is conducted at a temperature ranging from about 120°C to about 260°C.

Embodiment 17. The method described in the Summary of the Invention for preparing a polyester of Formula 1, wherein the diol of Formula 2 is C5-Q6 alkyldiol, C5-

Ci6 cycloalkylalkyldiol, or mixtures thereof.

Embodiment 18. The method of Embodiment 17, wherein the diol of Formula 2 is selected from the group consisting of 1,5-pentanediol, 1,6-hexanediol,

1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol,

1 , 16-hexadecanediol, 1 ,3-cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol,

1 ,4-cyclohexanediethanol, 1 ,4-cyclohexanedipropanol, and mixtures thereof Embodiments of the present invention as described in the Summary of the Invention include any other embodiments described herein, can be combined in any manner, and the descriptions of variables in the embodiments pertain not only to the methods of the present invention but also to polyesters produced from therefrom.

The invention is described in detail hereinunder.

As shown in Scheme 1, in a method of the present invention, a polyester of Formula 1 is prepared by contacting a diol of Formula 2, a ruthenium catalyst of Formula 3 and optionally a solvent or solvent system.

Scheme 1

Diols

A variety of diols of Formula 2 can be used in the process of the present invention including C5-Q6 alkyldiols (when A is -(CH₂)p-Wq- (CH₂)_r -, q is 0, and the sum of p and r is an integer of from 3 to 14) and C5-C16 cycloalkylalkyldiols (when q is 1).

Examples of suitable C C^ alkyldiols are 1,5-pentanediol, 1,6-hexanediol, 1,7- heptanediol, 1,8-octanediol, 1 ,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-tetradecanediol, or 1 , 16-hexadecanediol.

Examples of C5-C15 cycloalkylalkyldiols are 1 ,2-cyclopropanedimethanol,

1.2- cyclobutanedimethanol, 1 ,3-cyclopentanedimethanol, 1 ,2-cyclohexanedimethanol,

1.3- cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, 3-(hydroxymethyl)cyclohexane- ethanol, 1 ,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, 1 ,4-cyclohexanediethanol,

1.4- cyclohexanedipropanol, bicyclo[2.2.1]heptane-2,3-dimethanol, bicyclo[2.2.2]octane- 1 ,4-dimethanol, bicyclo[2.2.2]octane-2,3-dimethanol, or octahydro-4,7-methano-lH-indene-

2.5- dimethanol (CAS 28132-01-6), or 1,3-admantane-dimethanol (CAS 17071-62-4).

Mixtures of the aforementioned diols may also be used in the present method.

Preferred diols include 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,3-cyclohexane- dimethanol, 1 ,4-cyclohexanedimethanol, 1 ,4-cyclohexanediethanol, 1 ,4-cyclohexanedipropanol, or mixtures thereof.

In one embodiment of the invention, the diol of Formula 2 is selected from the group consisting of 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,3-cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, 1 ,4-cyclohexanediethanol, 1 ,4-cyclohexanedipropanol, and mixtures thereof.

Ru Catalyst

The method of the invention is catalyzed by a ruthenium (Ru) complex of Formula 3, requiring no base or acid promoter

a preferred embodiment, the Ru catalyst is represented by the compound of Formula

3a

wherein each of R1 and R^ is independently selected from the group consisting of alkyl, cycloalkyl, aryl, arylalkyl, heterocyclyl and heteroaryl.

In another embodiment, the compound of Formula 3a, wherein R¹ is t-butyl and R³ is ethyl as represented by the compound of Formula 3b, which is commercially available from Strem Chemical Inc.

3b

It is understood that when the catalyst includes one or more chiral centers, all stereoisomers are included in the scope of this invention.

The method of the invention is typically conducted in the presence of the ruthenium catalyst in an amount of about 0.05 mol% to about 5 mol%, or about 0.1 mol% to about 1 mol%, or about 0.2 mol% to about 0.8 mol% per mole of the diol of Formula 2.

Reaction Solvent

The methods of the present invention can be conducted in the presence of a solvent or a solvent system. The "solvent system" as referred herein means that it can be a mixture of more than one solvent. Preferably, the solvent system forms a homogenous solution and is anhydrous. Non-limiting examples of suitable solvents are cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, anisole, mesitylene, tetrahydrofuran (THF), 1 ,2-dimethoxyethane, 1,4-dioxane, diglyme, dimethylformamide (DMF), dimethylsulfoxide (DMSO), or mixtures thereof.

The methods of the present invention can also be conducted in a solventless condition.

The term "solventless" or "solvent-free" can be used interchangeably herein; it means that in the method of the invention, the reaction mixture contains less than 0.1% by weight, preferably less than 0.01% by weight of a solvent, based on the total weight of the reaction mixture. Mode of combination

The method of Scheme 1 is typically carried out a mixture of the diol of Formula 2 and the Ru catalyst of Formula 3 in the absence or in the presence of a solvent or a solvent system.

For operational ease, the diol of Formula 2 is added into the reaction vessel first. The

Ru catalyst of Formula 3 is typically added to the reaction vessel containing the diol of Formula 2 at room temperature under the an inert atmosphere such as nitrogen or Ar. If a solvent or a solvent system is employed, it is to be added last.

As shown in Scheme 1, the reaction forms molecular hydrogen as a byproduct. As the reaction is typically conducted at an elevated temperature, most of the hydrogen formed evolves from the reaction mixture as a gas. The reaction is typically conducted under a constant stream of inert gas at normal pressure (about 1 bar), and the hydrogen formed during the course of the reaction can be swept off to avoid building up of high hydrogen concentration in the reaction vessel.

The reaction temperature is not particularly limited, provided that it is at least 10°C less than the boiling point of the diols to avoid loss of reactant. If a solvent or a solvent system is present, the reaction temperature may go as high as the refluxing temperature of the reaction mixture. The reaction temperature is typically between about 100°C to about 300°C, preferably, is between about 120°C to about 260°C.

How long the reaction is carried out can be determined appropriately by one skilled in the art, which depends on the batch size and the reaction temperature to be employed.

The products of Formula 1 can be isolated by standard techniques known in the art. As the products of Formula 1 are typically solids at ambient temperature, they are generally isolated by filtration, optionally followed by rinsing with one or more organic solvents, e.g., hexane, methanol, ethanol, etc., to remove the unreacted diol, and then dried in an oven at 30-100°C with or without reduced pressure. The method of the present invention is further illustrated by Examples 1-12 below.

EXAMPLES

The abbreviation "E" stands for "Example" and "C" stands for "Comparative Example" is followed by a number indicating in which example the polyester is prepared. The examples were all prepared and tested in a similar manner.

Materials

All diols and solvents were commercially available from TCI, Sigma Aldrich, Alfa Aesar, or SCRC, and used as received without further purification. Xylenes is a mixture of 60% of m-xylene, 14% of p-xylene, 9% of o-xylene, and 17% of ethylbenzene. The ruthenium (Ru) catalyst (Milstein catalyst, carbonlyhydrido[6-(di-t-butylphpsphino- methylene)-2-(N,N-diethylamino-methyl)- 1 ,6-dihydropyridine]ruthenium(II), 98%, CAS No. 863971-63-5) was purchased from Strem Chemical Inc. Test Methods

1H NMR spectra were recorded using a Bruker 400MHz Advance II spectrometer. The testing sample was dissolved in CDCI₃. The chemical shifts were reported in ppm downfield from tetramethylsilane (TMS) and the coupling constants in Hz; "s" means singlet, "d" means doublet, "t" means triplet, "q" means quartet, "m" means multiplet.

FTIR spectra were obtained using a Nicolet NEXUS 5700 & Continuum Microscope; Method: diamond ATR mode; detector: DTGS; spectrum range: 4000 ~ 400 cm^"1.

GPC measurements were conducted with a Gel Permeation Chromatography (GPC) instrument using eAlliance 2695/2414 RI detector at 35°C. THF is the eluent and the injection flow speed is 1 mL/min. Embodiments of the present invention are further defined in the following Examples. Before every measurement, the GPC instrument was calibrated with standard polystyrene samples. The test sample was dissolved in THF at a concentration of ~ 3 mg/mL .

Differential scanning calorimetry (DSC) was carried out with a TA Q100 differential scanning calorimeter in a dry nitrogen atmosphere. The sample was first heated to 200°C at a heating rate of 10°C/min, and held at this temperature for 5 min to remove the thermal history, followed by quenching to 0°C. A heating rate of 10°C/min was used for the 2^nd time heating, and T_m (melting point) was taken on this round for all testing samples. T_c is the crystallization temperature which can be assessed by observing the temperature at which the maximum exotherm (heat release during crystallization) occurred on cooling from melt temperature 200°C, with a cooling rate of 10°C/min.

General Procedure for the Preparation of Polyester

A diol and the Ru catalyst were weighed and placed in a round bottom flask. The reactions were protected with N₂ gas by either attaching a N₂ balloon to the flask or sweeping a slow stream of N₂ flow by a gas inlet connector.

The mixture of the diol, the Ru catalyst and optional solvent(s) was heated to a temperature between 100°C and 300°C. The reaction proceeded with molecular hydrogen liberation as seen by the bubbles evolution. The reaction mixture was heated for at least 1 hour, typically for 8 hours or more. After the specified reaction time period, the mixture was allowed to cool down to room temperature; the reaction mixture generally solidified regardless of the extent of the dehydrogenative polymerization process.

The resulting reaction mixture was rinsed with ethanol (about 50 mL) and then washed with 50 mL of ethanol twice to remove the unreacted diol and/or oligomers. The remaining solids were isolated by filtration and dried in a vacuum oven at 50°C for overnight, and weighed to calculate the product yield. The polyester product was characterized by 1H NMR, FTIR, GPC and DSC.

The embodiment of the present invention is further defined in the following Examples. Example 1 : Preparation of polyesters from 1,5-pentanediol 1,5-Pentanediol (2.982 g, 30 mmol) and the Ru catalyst (47.4 mg, 0.1 mmol) were weighed and added to a 2-neck reaction flask (50 mL), fitted with a condenser. The reaction mixture was heated at 230°C with magnetic stirring for 8 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.791 g of polyesters of the present invention (60% yield).

1H NMR (CDCI3, 400 MHz): δ 1.42-1.90 (m, 4H, -CH₂-), δ 2.32 (t, 2H, -CH₂-COO-), δ 4.10 (t, 2H, -COO-CH₂-).

FTIR: 3443.9, 2956.4, 2873.7, 1732.6, 1457.7, 1419.7, 1388.9,1384.9, 1326.2, 1280.4,

1254.3, 1182.1, 1069.2, 1046.3, 977.4, 750.8 cm^"1.

GPC: M_n = 6800 g/mol, PDI = 1.7.

DSC: T_m= 24.9°C, T_c = -0.5°C.

Example 2: Preparation of polyesters from 1,10-decanediol 1,10-Decanediol (1.760 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 180°C for 9.5 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.34 g of polyesters of the present invention (76% yield).

1H NMR (CDC1_3, 400 MHz): δ 1.25-1.42 (m, 10 H, -CH₂-), δ 1.5-1.7 (m, 4H, -CH₂-), δ 2.32

(t, 2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3447.0, 2923.9, 2852.4, 1733.7, 1472.3, 1415.6, 1397.6, 1376.1, 1354.5, 1294.3, 1244.8, 1215.1, 1174.6, 1118.5, 1078.3, 1048.5, 1008.6, 957.6, 920.8, 821.6, 747.2, 722.7, 581.7 cm^"1.

GPC: M„= 8000 g/mol, PDI = 1.6

DSC: T_m= 68.7°C, T_c = 57.8°C.

Example 3: Preparation of polyesters from 1, 10-decanediol 1,10-Decanediol (1.760 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 180°C for 24 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.24 g of polyesters of the present invention (70%> yield).

1H NMR (CDCl_3, 400 MHz): δ 1.25-1.42 (m, 10 H, -CH₂-), δ 1.5-1.7 (m, 4H, -CH₂-), δ 2.32 (t, 2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-). FTIR: 3447.7, 2924.2, 2852.7, 1733.6, 1472.4, 1415.7, 1397.9, 1376.1, 1354.9, 1294.6, 1244.9, 1215.5, 1175.1, 1118.2, 1078.5, 1048.7, 1008.9, 958.0, 921.0, 821.6, 747.3, 722.8, 582.2 cm^"1.

GPC: M„= 7000 g/mol, PDI = 1.7

DSC: T_m= 68.1°C, T_c = 57.4°C.

Example 4: Preparation of polyesters from 1,10-decanediol 1,10-Decanediol (1.760 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 230-240°C for 9 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.05 g of polyesters of the present invention (59% yield).

(t, 2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3447.9, 2923.1, 2852.3, 1733.6, 1472.2, 1415.6, 1398.0, 1376.1, 1354.7, 1294.3,

1244.8, 1215.2, 1175.1, 1118.3, 1078.3, 1048.6, 1008.8, 958.0, 821.6, 747.2, 722.6,

581.8 cm^"1.

GPC: M_n = 5250 g/mol, PDI = 1.4.

DSC: T_m= 66.5°C, T_c = 56.2°C.

Example 5: Preparation of polyesters from 1,10-decanediol

1,10-Decanediol (1.917 g, 11 mmol) and the Ru catalyst (10 mg, 0.022 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 180°C for 9 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.048 g of polyesters of the present invention (55% yield).

¹H NMR (CDC1_3, 400 MHz): δ 1.25-1.42 (m, 10H, -CH₂-), δ 1.5-1.7 (m, 4H, -CH₂-), δ 2.32

(t, 2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3446.2, 2922.5, 2852.2, 1733.7, 1472.4, 1415.5, 1398.6, 1376.1, 1354.5, 1294.5, 1244.8, 1215.2, 1175.3, 1118.4, 1077.8, 1048.4, 1009.5, 957.5, 821.4, 747.0, 722.4,

582.1 cm^"1.

GPC: M„= 2800 g/mol, PDI = 1.3.

DSC: T_m= 62.4°C, T_c = 52.4°C.

Example 6: Preparation of polyesters from 1,10-decanediol 1,10-Decanediol (3.86 g, 22 mmol) and the Ru catalyst (10 mg, 0.022 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 180°C for 12.5 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 2.09 g of polyesters of the present invention (54% yield).

1H NMR (CDC1_3, 400 MHz): δ 1.25-1.42 (m, 16 H, -CH₂-), δ 1.5-1.7 (m, 8H, -CH₂-), δ 2.32 (t, 2H, -CH₂-COO-), δ 3.65 (t, 2 H,-CH₂-OH), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3325.8, 2921.4, 2851.9, 1733.6, 1472.1, 1415.3, 1399.5, 1376.1, 1354.8, 1294.3, 1244.8, 1215.3, 1175.8, 1118.2, 1077.1, 1048.4, 1010.8, 957.7, 921.1, 821.5, 746.8, 722.2, 582.4 cm^"1.

GPC: M„= 2300 g/mol, PDI = 1.3.

DSC: T_m= 63.4°C, T_c = 49.0°C.

Example 7: Preparation of polyesters from 1,10-decanediol 1,10-Decanediol (7.72 g, 44 mmol) and the Ru catalyst (10 mg, 0.022 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 180°C for 12.5 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 4.69 g of polyesters of the present invention (64% yield).

1H NMR (CDC1_3, 400 MHz): δ 1.25-1.42 (m, 16 H, -CH₂-), δ 1.5-1.7 (m, 8H, -CH₂-), δ 2.32 (t, 2H, -CH₂-COO-), δ 3.65 (t,2 H,-CH₂-OH), δ 4.07 (t, 2H, -COO-CH₂-).

GPC: M„= 1960 g/mol, PDI = 1.5.

DSC: T_m= 60.8°C, T_c = 48.1°C.

Comparative Example 1 : Preparation of polyesters from 1,10-decanediol

1,10-Decanediol (19.3 g, 110 mmol) and the Ru catalyst (5 mg, 0.011 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa and connected with a N₂ balloon. The reaction mixture was heated at 180°C for 11.5 hr. The resulting crude mixture was rinsed with ethanol. No solid was isolated after rinsing with ethanol.

Example 8: Preparation of polyester from 1,12-dodecanediol 1,12-Dodecanediol (1.78 g, 8.8 mmol) and the Ru catalyst (20 mg, 0.022 mmol) were weighed and added to a single neck reaction flask (50 mL). The reaction flask was then sealed with a rubber septa, connected with a N₂ balloon. The reaction mixture was heated at 150°C for 48 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.33 g of polyesters of the present invention (75 %> yield). 1H NMR (CDC1_3, 400 MHz): δ 1.29 (m, 14 H, -CH₂-), δ 1.62-1.64 (m, 4H, -CH₂-), δ 2.32 (t,

2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3448.7, 2919.4, 2850.9, 1733.3, 1471.8, 1415.4, 1397.6, 1367.0, 1329.8, 1287.0,

1271.4, 1232.2, 1206.1, 1174.8, 1118.4, 1086.2, 1061.9, 1033.0, 997.1, 958.2, 921.2, 794.8, 732.6, 582.5 cm^"1.

GPC: M_n = 3740 g/mol, PDI = 2.4.

DSC: T_m= 76.4°C, T_c = 62.6°C.

Example 9: Preparation of polyesters from 1,10-decanediol 1,10-Decanediol (1.76 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a 2-neck reaction flask (50 mL) fitted with a condenser and a connector on top for N₂ stream inlet. After 3 mL of toluene (degassed before use) was added, the reaction mixture was heated at 135°C with magnetic stirring for 24 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.53 g of polyesters of the present invention (87% yield).

1H NMR (CDC1_3, 400 MHz): δ 1.31 (m, 10 H, -CH₂-), δ 1.6-1.7 (m, 4H, -CH₂-), δ 2.32 (t, 2H,

-CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3447.8, 2924.7, 2852.7, 1733.7, 1472.4, 1415.6, 1397.6, 1376.1,1354.4,1294.3,

1244.8, 1215.1, 1174.8, 1118.5, 1078.4, 1048.5, 1008.5, 957.5, 921.1, 857.3,

747.3,722.6, 582.4 cm^"1.

GPC: M_n =7000 g/mol, PDI=1.7.

DSC: T_m= 72.3°C, T_c = 57.9°C.

Comparative Example 2: Preparation of polyesters from 1,10-decanediol 1,10-decanediol (1.76 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a 2-neck reaction flask (50 mL) fitted with a condenser and a connector on top for N₂ stream inlet. After 5 mL of toluene (degassed before use) was added, the reaction mixture was heated at 135°C with magnetic stirring for 24 hr. The resulting crude mixture was rinsed with ethanol. No solid was obtained after rinsing with ethanol.

Example 10: Preparation of polyesters from 1,10-decanediol 1,10-Decanediol (1.76 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a 2-neck reaction flask (50 mL) fitted with a condenser and a connector on top for N₂ stream inlet. After 1 mL of DMF (degassed before use) was added, the reaction mixture was heated at 150°C with magnetic stirring for 24 hr. The resulting crude mixture was precipitated and rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 0.445 g of polyesters of the present invention (25% yield). 1H NMR (CDCI3, 400 MHz): δ 1.31(m, 10 H, -CH₂-), δ 1.61-1.65 (m, 4H, -CH₂-), δ 2.32 (t,

2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

1244.8, 1215.1, 1174.8, 1118.5, 1078.4, 1048.5, 1008.5, 957.5, 921.1, 857.3, 747.3, 722.6, 582.4 cm^"1.

GPC: M_n = 2500 g/mol, PDI = 1.1.

DSC: T_m= 64.0°C, T_c = 52.0°C.

Comparative Example 3: Preparation of polyester from 1,10-decanediol 1,10-Decanediol (1.76 g, 10 mmol) and the Ru catalyst (22.6 mg, 0.05 mmol) were weighed and added to a 2-neck reaction flask (50 mL) fitted with a condenser and a connector on top for N₂ stream inlet. After 5 mL of DMF (degassed before use) was added, the reaction mixture was heated at 150°C with magnetic stirring for 24 hr. The resulting crude mixture was rinsed with ethanol. No solid was obtained after rinsing with ethanol.

Example 11 : Preparation of polyester from 1 ,12-dodecanediol 1,12-Dodecanediol (1.78 g, 8.8 mmol) and the Ru catalyst (20 mg, 0.044 mmol) were weighed and added to a 2-neck reaction flask (50 mL) fitted with a condenser and a connector on top for N₂ stream inlet. After 2 mL of xylenes (degassed before use) was added, the reaction mixture was heated at 150°C with magnetic stirring for 48 hr. The resulting crude mixture was rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.602 g of polyesters of the present invention (90% yield).

1H NMR (CDC1_3, 400 MHz): δ 1.29 (m, 14 H, -CH₂-), δ 1.62-1.64 (m, 4H, -CH₂-), δ 2.32 (t,

2H, -CH₂-COO-), δ 4.07 (t, 2H, -COO-CH₂-).

FTIR: 3448.2, 2919.0, 2850.7, 1732.9, 1468.8, 1415.5, 1397.1, 1366.8, 1329.7, 1271.2, 1232.2, 1205.9, 1173.9, 1117.4, 1086.0, 1062.0, 1033.1, 997.2, 958.2, 921.0, 794.7,

721.9, 582.7 cm^"1.

GPC: M„= 22000 g/mol, PDI = 1.9.

DSC: T_m= 80.7°C, T_c = 64.4°C

Example 12: Preparation of polyester from 1 ,4-cyclohexanedimethanol 1 ,4-cyclohexanedimethanol (1.3 g, 8.8 mmol) and the Ru catalyst (20 mg, 0.044 mmol) were weighed and added to a 2-neck reaction flask (50 mL) fitted with a condenser and a connector on top for N₂ stream inlet. After 2 mL of xylenes (degassed before use) was added, the reaction mixture was heated at 150°C with magnetic stirring for 48 hr. The resulting crude mixture was precipitated and rinsed with ethanol. The rinsed solids were isolated by filtration and dried at 50°C under reduced pressure overnight to afford 1.17 g of polyesters of the present invention (90% yield). 1H NMR (CDC1₃, 400 MHz): δ 1.21-1.92 (m, 8H); δ 2.03-2.59 (m, 2H), δ 3.90- 4.02 (m, 2H, -COO-CH₂-)

FTIR: 3438.6, 2936.5, 2857.6, 1727.9, 1450.8, 1391.6, 1321.0, 1249.8, 1230.2, 1 175.8,

1 138.2, 1037.0, 933.2, 899.5, 770.0, 673.9, 597.7cm^"1.

GPC: M_n = 3280 g/mol, PDI = 2.0.

DSC: T_g=30.8°C, T_m=150.7°C.

The reaction parameters of examples 1-12 and comparative examples 1-3 are summarized in Table 1.

Table 1

Examples 1-12 demonstrated that the inventive process is suitable for the dehydrogenative polyesterification of a variety of diols of Formula 2 to provide the respective aliphatic polyesters. In addition, there is no particular limitation on reaction temperature which spanned a wide range (i.e. from 135°C for E9 to 240°C for E4). Similar conclusion was obtained for reaction time ranging from 8 hr to 48 hr.

In summary, the method of this invention has great commercial potential for the production of a wide variety of aliphatic polyesters with low effective catalyst loading and provides a much cleaner process with high atom economy compared to conventional polyesterification methods.

While the invention has been illustrated and described in typical embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions are possible without departing from the spirit of the present invention. As such, modifications and equivalents of the invention herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the invention as defined by the following claims.

Claims

CLAIMS What is claimed is:

1. A method for preparing a polyesters of Formula 1,

1

comprising:

(a) combining a diol of Formula 2, a ruthenium catalyst of Formula 3

and optionally a solvent or a solvent system to form a reaction mixture; and

(b) heating the reaction mixture at a temperature in the range of 100-300°C for 1-60 hours to form the polyesters of Formula 1;

wherein

A is -(CH₂)p-Wq- (CH₂)_r -, where W is selected from the group consisting of C₃-C₁₀ cycloalkyl, p is an integer of from 1 to 8, q is 0 or 1 , r is an integer of from 1 to 8, and when q is 0, then the sum of p and r is an integer of from 3 to 14;

the sum of k and n is an integer of from 10 to 150;

P(OR2)₂, N(R3)₂;

L₃ is a mono-dentate two-electron donor selected from the group consisting of CO, P(R²)₃, P(0R3)₃, NO⁺, nitrile (R⁴CN) and isonitrile (R⁵NC);

R¹ , R², R³, R⁴and R⁵ are each independently selected from the group consisting of alkyl, cycloalkyl, aryl, alkylaryl, heterocyclyl and heteroaryl.

2. The method of claim 1 , wherein is P(R¹)₂, L₂ is N(R³)₂, and L₃ is CO.

3. The method of claim 2, wherein R¹ is t-butyl, and R³ is ethyl.

4. The method of claim 1, wherein the amount of the ruthenium catalyst of Formula 3 is from about 0.05 mol% to about 5 mol% per mole of the diol.

5. The method of claim 1, wherein the diol of Formula 2 is C5-C16 alkyldiol, C5- Ci6 cycloalkylalkyldiol, or mixtures thereof.

6. The method of claim 5, wherein the diol of Formula 2 is selected from the group consisting of 1,5-pentanediol, 1 ,6-hexanediol, 1,8-octanediol, 1,10-decanediol,

1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,3-cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, 1 ,4-cyclohexanediethanol, 1 ,4-cyclohexanedipropanol, and mixtures thereof

7. The method of claim 1, wherein the solvent or the solvent system is selected from the group consisting of cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, anisole, mesitylene, tetrahydrofuran, 1 ,2-dimethoxyethane, 1,4-dioxane, diglyme, dimethylformamide, dimethylsulfoxide, and mixtures thereof.

8. The method of claim 1 , wherein the amount of the solvent or the solvent system is in the range of from about. 0.01 L to about 0.45 L per mole of the diol of Formula 2.

9. The method of claim 1, wherein the polyester of Formula 1 is formed in an inert gas atmosphere at a pressure from about 1 bar to aboiu 10 bar.

10. Polyesters of Formula 1 prepared by the method of any of claims 1-9 ,

wherein

A is -(CH₂)p-Wq- (CH₂)_r -, where W is selected from the group consisting of C₃-C₁₀ cycloalkyl, p is an integer of from 1 to 8, q is 0 or 1, r is an integer of from 1 to 8, and when q is 0, then the sum of p and r is an integer of from 3 to 14; and the sum of k and n is an integer of from 10 to 150.