Functional Aliphatic Polyesters Research Articles

Synthesis and Post-Functionalization of Poly(conjugated ester)s Based on 3-Methylene-1,5-dioxepan-2-one.

Poly(α-methylene ester)s are an attractive type of functional aliphatic polyesters that represent a platform for the fabrication of various biodegradable and biomedical polymers. Herein, we report the controlled ring-opening polymerization (ROP) of a seven-membered α-methylene lactone (3-methylene-1,5-dioxepan-2-one, MDXO) that was synthesized based on the Baylis-Hillman reaction. The chemoselective ROP of MDXO was catalyzed by diphenyl phosphate (DPP) at 60 °C or stannous octoate (Sn(Oct)2) at 130 °C, generating α-methylene-containing polyester (PMDXO) with a linear structure and easily tunable molar mass. The ring-opening copolymerization of MDXO with ε-caprolactone or 1,5-dioxepan-2-one was also performed under the catalysis of DPP or Sn(Oct)2 to afford copolymers with different compositions and sequence structures that are influenced by the kinds of monomers and catalysts. PMDXO is a slowly crystallizable polymer with a glass transition temperature of ca. -33 °C, and its melting temperature and enthalpy are significantly influenced by the thermal history. The thermal properties of the copolymers are dependent on their composition and sequence structure. Finally, the post-modification of PMDXO based on the thiol-Michael addition reaction was briefly explored using triethylamine as a catalyst. Given the optimized condition, PMDXO could be dually modified to afford biodegradable polyesters with different functionalities.

Ring‐Opening Polymerization of a Benzyl‐Protected Cyclic Ester towards Functional Aliphatic Polyester†

Comprehensive SummaryMonomer design strategy has become a powerful tool to access polymers with desired and diverse functionalities. Here, we designed a novel monomer 2‐((benzyloxy)methyl)‐1,4‐oxathiepan‐7‐one (BTO) via installing a benzyl ether side chain to the structure of 1,4‐oxathiepan‐7‐one (OTO). The ring‐opening polymerization of BTO with Zn1 as the catalyst demonstrated the characteristics of living polymerization with turnover frequency (TOF) up to 2520 h−1. With a [BTO]0/[Zn1]0/[I]0 feed ratio of 2000/2/1, polymer with high number‐average molecular weight (Mn = 536 kDa) and narrow dispersity (Ð = 1.06) was obtained. The produced polymer with a glass transition temperature of ‐17°C behaved as an elastomer at room temperature. Consequently, the monomer BTO was copolymerized with L‐LA to modulate the mechanical properties of P(L‐LA). When the BTO content is 10%, the copolymer exhibits excellent strength (24 MPa) and elongation at break (270%), affording a crystalline, hard, and tough plastic material that combines the high ductility of P(BTO) and the high modulus of P(L‐LA). In addition, the oxidation of P(BTO) to P(BTO)‐SO2 led to an improvement of Tg from ‐17°C to 38°C. Debenzylation of P(BTO)‐SO2 afforded P(BTO)‐SO2‐OH containing free hydroxyl groups. Ultimately, P(BTO) could be hydrolyzed under a base condition to recover the corresponding hydroxyl acid intermediate, which could be used to prepare the monomer again and complete the closed‐loop from monomer to polymer to monomer.

Progress in the Preparation of Functional and (Bio)Degradable Polymers via Living Polymerizations.

This review presents the latest developments in (bio)degradable approaches and functional aliphatic polyesters and polycarbonates prepared by typical ring-opening polymerization (ROP) of lactones and trimethylene carbonates. It also considers several recent innovative synthetic methods including radical ring-opening polymerization (RROP), atom transfer radical polyaddition (ATRPA), and simultaneous chain- and step-growth radical polymerization (SCSRP) that produce aliphatic polyesters. With regard to (bio)degradable approaches, we have summarized several representative cleavable linkages that make it possible to obtain cleavable polymers. In the section on functional aliphatic polyesters, we explore the syntheses of specific functional lactones, which can be performed by ring-opening copolymerization of typical lactone/lactide monomers. Last but not the least, in the recent innovative methods section, three interesting synthetic methodologies, RROP, ATRPA, and SCSRP are discussed in detail with regard to their reaction mechanisms and polymer functionalities.

Organocatalyzed ring-opening copolymerization of α-bromo-γ-butyrolactone with ε-caprolactone for the synthesis of functional aliphatic polyesters – pre-polymers for graft copolymerization

ABSTRACTDiphenyl phosphate (DPP) was exploited as an organocatalyst to synthesize copolymers by ring-opening polymerization with α-bromo-γ-butyrolactone (αBrγBL) and ε-caprolactone (εCL) as monomers and polyethylene glycol (PEG) as initiator. The conversion rates of monomers and molecular weights of copolymers synthesized under different conditions were determined by 1H-NMR. The 1H-NMR results showed that the copolymers of αBrγBL and εCL initiated by PEG (PEGCB) were successfully synthesized and the conversions of εCL were relatively high (＞70%), while the conversions of αBrγBL were relatively low (＜26%). The highest molar ratio of αBrγBL to εCL units in these copolymers is 0.17, when the copolymerization was carried out at 100℃ for 17h.The bromine atoms hanged on the chain of the copolymers PEGCB provide a good opportunity to construct graft copolymers via atom transfer radical polymerization (ATRP). The subsequent grafting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) was conducted by using PEGCB3 as macroinitiator, CuBr/N,N’,N’,N”,N”- pentamethyldiethylenetriamine (PMDETA) as catalysts and toluene/anisole as solvents via ATRP. According to the analysis of 1H-NMR, the grafting efficiency, grafting ratio and grafting frequency were 22.4%, 160.7% and 1133.8, respectively.

Radical Copolymerization of Vinyl Ethers and Cyclic Ketene Acetals as a Versatile Platform to Design Functional Polyesters

AbstractFree‐radical copolymerization of cyclic ketene acetals (CKAs) and vinyl ethers (VEs) was investigated as an efficient yet simple approach for the preparation of functional aliphatic polyesters. The copolymerization of CKA and VE was first predicted to be quasi‐ideal by DFT calculations. The theoretical prediction was experimentally confirmed by the copolymerization of 2‐methylene‐1,3‐dioxepane (MDO) and butyl vinyl ether (BVE), leading to rMDO=0.73 and rBVE=1.61. We then illustrated the versatility of this approach by preparing different functional polyesters: 1) copolymers functionalized by fluorescent probes; 2) amphiphilic copolymers grafted with poly(ethylene glycol) (PEG) side chains able to self‐assemble into PEGylated nanoparticles; 3) antibacterial films active against Gram‐positive and Gram‐negative bacteria (including a multiresistant strain); and 4) cross‐linked bioelastomers with suitable properties for tissue engineering applications.

Radical Copolymerization of Vinyl Ethers and Cyclic Ketene Acetals as a Versatile Platform to Design Functional Polyesters.

Free-radical copolymerization of cyclic ketene acetals (CKAs) and vinyl ethers (VEs) was investigated as an efficient yet simple approach for the preparation of functional aliphatic polyesters. The copolymerization of CKA and VE was first predicted to be quasi-ideal by DFT calculations. The theoretical prediction was experimentally confirmed by the copolymerization of 2-methylene-1,3-dioxepane (MDO) and butyl vinyl ether (BVE), leading to rMDO =0.73 and rBVE =1.61. We then illustrated the versatility of this approach by preparing different functional polyesters: 1) copolymers functionalized by fluorescent probes; 2) amphiphilic copolymers grafted with poly(ethylene glycol) (PEG) side chains able to self-assemble into PEGylated nanoparticles; 3) antibacterial films active against Gram-positive and Gram-negative bacteria (including a multiresistant strain); and 4) cross-linked bioelastomers with suitable properties for tissue engineering applications.

New Chemistry in Functional Aliphatic Polyesters

Aliphatic polyesters are important biodegradable polymers with wide applications. Polyesters prepared by ring-opening polymerization often have a limited range of properties, because of the minimal functional diversity of available lactone monomers. In this review, synthetic strategies in preparing functional lactone monomers are highlighted, as well as recent controlled polymerization strategies to synthesize functional aliphatic polyesters, which include proton-transfer polymerization, ring opening polymerization of O-carboxyanhydrides, radical ring-opening polymerization of cyclic ketene acetals, and copolymerization of epoxide/anhydride.

Establishing α-bromo-γ-butyrolactone as a platform for synthesis of functional aliphatic polyesters – bridging the gap between ROP and SET-LRP

Utilizing α-bromo-γ-butyrolactone (αBrγBL) as a comonomer with ε-caprolactone (εCL) or l-lactide (LLA) produces copolymers with active and available grafting sites, e.g., for SET-LRP, where the choice of the grafting monomers is limited only by one's imagination.

Regioselective Halogenation of Poly(lactide) by Free‐Radical Process

Modification of the biodegradable and renewable poly(lactide) (PLA) to provide functional aliphatic polyesters is highly desirable to meet application requirements. In this context, the objective of this work is to evaluate the possibility of using free‐radical substitution as a simple and non‐degrading method to yield the desired functional PLA. Halogenation of PLA is carried out in solution and various reaction conditions are evaluated. Halogenated PLAs are characterized by 1H NMR spectroscopy and size exclusion chromatography (SEC) to evaluate the substitution ratios and to check the non‐degrading character of the radical modification. Furthermore, reactions on model compounds as well as MALDI‐TOF analyses are performed to elucidate the involved mechanism. The combined results prove the free‐radical halogenation of PLA in solution to be regioselective with only the ω‐halogenated PLA being obtained without main‐chain substitution.

Synthesis, characterization, and hydrolytic degradation of graft copolymers of polystyrene and aliphatic polyesters

In the present study, a new class of biodegradable graft copolymers of polystyrene (PS) with aliphatic polyester (APE) side chains were synthesized through combination of nitroxide-mediated free radical polymerization (NMRP) and ring-opening polymerization (ROP) with copper (I)-catalyzed ‘click’ chemistry. First, the click component, azido-functional PS (PS-N3) was prepared by copolymerization of styrene and chloromethyl styrene by NMRP followed by the conversion of chlorine groups of the resulting copolymer to azido groups by using NaN3 in N,N-dimethylformamide. Propargyl functional APEs were prepared independently by ROP of lactic acid and glycolic acid using tin octoate in the presence of propargyl alcohol at 130 °C. Finally, PS-N3 was coupled with the resulting polymers by click chemistry to yield graft copolymers (PS-g-poly (L-lactic-co-glycolic acid) [PLLA] and PS-g-PLLGA, respectively). The intermediates and final graft copolymers were characterized by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectral and gel permeation chromatography analyses. The hydrolytic degradation behavior of the obtained graft copolymers in phosphate buffer saline solution were investigated by the weight loss and molecular weight measurements. It is shown that both copolymers undergo slow hydrolytic degradation, PS-g-PGLLA being relatively faster due to the presence of hydrophilic glycolic acid groups in the structure.

Functional aliphatic polyesters and nanoparticles prepared by organocatalysis and orthogonal grafting chemistry

AbstractWe describe the use of organic catalysis for the ring‐opening polymerization of functionalized lactones and conversion of the resulting aliphatic polyesters into crosslinked nanoparticles that carry additional functional groups amenable to further modification. Specifically, highly functional aliphatic polyester homopolymers, as well as random and block copolymers, were prepared by 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene catalysis, giving polyesters with pendent alkene and alkyne groups. Azide‐alkyne click and thiol‐ene chemistries were used for postpolymerization modification of diblock copolymers possessing alkene groups on one block and alkyne groups on the other block. The polyesters were crosslinked using azide/alkyne cycloaddition, by reaction of α,ω‐diazides with the pendent alkynes on the polyester backbone. This gave polyester nanoparticles possessing alkene functionality, which were subjected to further modification using thiol‐ene reactions to introduce additional functionality. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Assessing the Degradation Profile of Functional Aliphatic Polyesters with Precise Control of the Degradation Products

The pre-polymer poly(but-2-ene-1,4-diyl malonate) (PBM) and a series of PBM-based materials are shown to be degradable under physiological conditions in vitro and they are therefore presented as potential materials for biomedical applications. Four different PBM-based materials are synthesized: a PBM homopolymer, crosslinked PBM with and without spacer, and a triblock copolymer of PBM and PLLA with the PBM as an amorphous middle block. The polymers are subjected to hydrolytic degradation in phosphate-buffered saline at pH = 7.4 and 37 °C. The results show that all the PBM-based materials degrade without a rapid release of acidic degradation products or any substantial lowering of the pH that might jeopardize their biocompatibility.

“Clip” and “Click” Chemistries Combination: Toward Easy PEGylation of Degradable Aliphatic Polyesters

α-Methoxy-ω-alkyne poly(ethylene glycol) (PEG) was tagged with pendent N-hydroxy-succinimidyl activated esters by photografting of a molecular clip. This easily synthesized heterofunctional PEG was found to be a versatile building block for (i) conjugation with an amino derivative and (ii) grafting to azido functional aliphatic polyesters backbone by Huisgen's 1,3-dipolar cycloaddition. This original combination of "clip" and "click" reactions provides a versatile and straightforward pathway for the synthesis of functional amphiphilic and degradable copolymers valuable for biomedical applications such as in drug-delivery.

Design of Elastomeric Homo- and Copolymer Networks of Functional Aliphatic Polyester for Use in Biomedical Applications

An unsaturated aliphatic polyester was synthesized by condensation polymerization to yield the pre-polymer, poly(but-2-ene-1,4-diyl malonate) (PBM), which is applicable as an elastomeric network and as a macroinitiator for the polymerization of cyclic ester monomers. The method of preparation was simple and straightforward with no need to purify the monomers or add a potentially harmful catalyst. The number average molecular weight of the pre-polymer could easily be increased from 5000 to 12000 by extending the reaction time. The pre-polymer PBM was successfully cross-linked with UV-radiation to form a clear, transparent, colorless, flexible, and strong film. PBM as a macroinitiator for l-lactide (LLA) and ε-caprolactone (CL) polymerizations highly increased the ductility of the LLA-polymer, while maintaining the strength, compared to PLLA polymerized with common initiators. The tensile properties of PCL were also improved. The linear PCL-PBM and PLLA-PBM polymers were easily cross-linked to give polymers with greater strength and higher modulus as the result.

Synthesis and properties of waterborne hyperbranched aliphatic polyester clear coats

A waterborne hyperbranched polyester (WHP) consisting of a multi-hydroxy functional aliphatic polyester core, which is endcapped with an epoxy group of CARDURA E10 and salt-like groups in different ratios was synthesized. The core was a second generation of hyperbranched aliphatic polyester Boltorn™ H20 with approximately 16 hydroxyl groups. The effects of different ratios of chemical structure of end groups were studied by evaluating various properties of WHP such as acid value, solubility in water and dynamic viscosity. A natural good control over the solubility of the samples was possible by salt-like functionality. Since acid value decreased as reaction time increased, it gave an indication of the end of the reaction when the change in acid value was small. The investigation of solubility characteristics of the modified hyperbranched polyester illustrated that those with higher concentration of salt-like groups were more soluble while those having less salt-like groups were less soluble. The viscosity of the resin WHP was reduced rapidly by diluting with water and raising the temperature. The performance of film, baking with waterborne hyperbranched polyester and hexamethoxy methyl melamine resin (HMMM) at 140 °C, was excellent. The glass transition temperature ( T g) of product decreased after modification. Therefore, the waterborne curable resins based on hyperbranched polyester were regarded as an alternative strategy as waterborne clear coats.

Soluble Camptothecin Derivatives Prepared by Click Cycloaddition Chemistry on Functional Aliphatic Polyesters

Aliphatic polyesters are of interest as biomaterials and drug-delivery vehicles, as their ability to degrade under physiological conditions provides a mechanism for both drug release and clearance of the polymer from the body. Presented here is the synthesis of a polyester-drug graft copolymer conjugate, enabled by click cycloaddition of azide-functionalized camptothecin derivatives with alkyne-functionalized aliphatic polyesters. Further grafting of residual alkyne groups with azide-terminated poly(ethylene oxide) gave a water-soluble polyester-camptothecin conjugate. Control over PEGylation and drug loading, inherent to the graft copolymer design, opens versatile routes to new materials with potential utility in polymer therapeutics.

Novel Aliphatic Polyesters Based on Functional Cyclic (Di)Esters

AbstractRecent progress in the chemical synthesis of novel aliphatic polyesters via ring‐opening polymerization of functional cyclic (di)esters are reviewed in this article. Syntheses of these functional aliphatic polyesters are being classified into three groups according to the structure of the cyclic monomers: (i) cyclic diesters, (ii) morpholine‐2,5‐dione derivatives, and (iii) cyclic esters. Progress in the synthesis and polymerization of monomers in each category is reported with an emphasis on controlled synthesis. The recent achievements have enabled the synthesis of a variety of novel aliphatic polyesters, including hydrophilic, halogenated, and unsaturated polyesters. Structure of the most common R‐functionalized cyclic precursors of aliphatic polyesters.magnified imageStructure of the most common R‐functionalized cyclic precursors of aliphatic polyesters.

Synthesis and properties of UV curable waterborne hyperbranched aliphatic polyester

The UV curable waterborne hyperbranched polyester (WBHP) consisting of a multi-hydroxy functional aliphatic polyester core, which is endcapped with methacrylic and salt-like groups in different ratios was synthesized. The core is second generation of hyperbranched aliphatic polyester Boltorn™ H20 with approximately 16 hydroxyl groups. The effects of different ratios of chemical structure of end groups were studied by evaluating various properties of WBHP such as solubility in water, dynamic viscosity, UV curing rate and final unsaturation conversion. A natural good control over the solubility of the samples was possible by salt-like functionality and raising the temperature. The investigation of solubility characteristics of the modified hyperbranched polyester illustrated that those with higher concentration of salt-like moiety were more soluble while those of having lower salt-like moiety were less soluble. The viscosity of the resin WBHP was reduced rapidly by dilution with water and raising temperature. Water showed a favorable viscosity reduction effect as compared to monomer and its blend with water. The polymerization rate of the resins under UV irradiation in the presence of a photoinitiator showed an increasing trend with higher concentration of methacrylate functionality.

New Functional Aliphatic Polyesters by Chemical Modification of Copolymers of ε-Caprolactone with γ-(2-Bromo-2-methylpropionate)-ε-caprolactone, γ-Bromo-ε-caprolactone, and a Mixture of β- and γ-Ene-ε-caprolactone

New functional aliphatic polyesters were prepared by chemical modification of brominated copolyesters. Poly(e-caprolactone)-co-poly(γ-(2-bromo-2-methylpropionate)-e-caprolactone) copolymer was prep...

Studies on copolymerization of succinic anhydride and allyl glycidyl ether

Functional aliphatic polyesters were synthesised by melt copolymerization of succinic anhydride (SA) and allyl glycidyl ether (AGE) in the presence of benzyltrimethylammonium chloride (BTMAC) as a catalyst. The influence of the parameters of the process: AGE/SA feed ratio, duration of the reaction, amount of water and of the catalyst added on the reaction course and on characteristics of the products obtained has been examined. Tendency to gelation of the polyesters during some syntheses and increase of molecular weight after consumption of functional groups were observed.