Synthesis and characterization of degradable triarm low unsaturated poly(propylene oxide)‐block‐polylactide copolymers

A series of novel degradable triarm poly(propylene oxide)‐block‐polylactide (PPO‐b‐PLA) copolymers was synthesized by ring‐opening polymerization of L ‐lactide (LLA) or D ,L ‐lactide (DLLA) using low unsaturated PPO triols as macromolecular initiator. The chemical structures of the resulting copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Combination of FTIR, GPC, and NMR results confirmed the formation of PPO‐b‐PLA copolymers. One glass transition was observed by differential scanning calorimetry (DSC), suggesting good miscibility between PPO and PLA segments in the copolymers. DSC and wide‐angle X‐ray diffraction demonstrated that PPO‐b‐PLLA copolymers were semicrystalline materials, and the crystallinity increased with increasing the PLLA content. In contrast, PPO‐b‐PDLLA copolymers were totally amorphous. The PPO‐b‐PLA copolymers exhibited improved thermal stability when compared with PPO polyols according to thermogravimetric analysis. The thermal degradation behavior of the copolymers depended on the composition. Polyurethane foams were prepared by crosslinking PPO and PPO‐b‐PLA copolymers using isocyanate. Alkaline degradation of the foams was investigated in 10 wt/vol % NaOH at 80°C. The results show that the novel PPO‐b‐PLA copolymers could be promising as degradable polymeric materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

AB‐ and ABC‐type di‐ and triblock copolymers of poly[styrene‐block‐(ε‐caprolactone)] and poly[styrene‐block‐(ε‐caprolactone)‐block‐lactide]: synthesis,characterization and thermal studies

Polystyrene terminated with benzyl alcohol units was employed as a macroinitiator for ring‐opening polymerization of ε‐caprolactone and L ‐lactide to yield AB‐ and ABC‐type block copolymers. Even though there are many reports on the diblock copolymers of poly(styrene‐block‐lactide) and poly(styrene‐block‐lactone), this is the first report on the poly(styrene‐block‐lactone‐block‐lactide) triblock copolymer consisting of two semicrystalline and degradable segments. The triblock copolymers exhibited twin melting behavior in differential scanning calorimetry (DSC) analysis with thermal transitions corresponding to each of the lactone and lactide blocks. The block derived from ε‐caprolactone also showed crystallization transitions upon cooling from the melt. In the DSC analysis, one of the triblock copolymers showed an exothermic transition well above the melting temperature upon cooling. Thermogravimetric analysis of these block copolymers showed a two‐step degradation curve for the diblock copolymer and a three‐step degradation for the triblock copolymer with each of the degradation steps associated with each segment of the block copolymers. The present study shows that it is possible to make pure triblock copolymers with two semicrystalline segments which also consist of degradable blocks. Copyright © 2009 Society of Chemical Industry     

Nondegradative additive manufacturing of medical grade copolyesters of high molecular weight and with varied elastic response

Although additive manufacturing through melt extrusion has become increasingly popular as a route to design scaffolds with complex geometries the technique if often limited by the reduction in molecular weight and the viscoelastic response when degradable aliphatic polyesters of high molecular weight are used. Here we use a melt extruder and fused filament fabrication printer to produce a reliable nondegradative route for scaffold fabrication of medical grade copolymers of L-lactide, poly(ε-caprolactone-co-L-lactide), and poly(L-lactide-co-trimethylene carbonate). We show that degradation is avoided using filament extrusion and fused filament fabrication if the process parameters are deliberately chosen based upon the rheological behavior, mechanical properties, and polymer composition. Structural, mechanical, and thermal properties were assessed throughout the process to obtain comprehension of the relationship between the rheological properties and the behavior of the medical grade copolymers in the extruder and printer. Scaffolds with a controlled architecture were achieved using high-molecular-weight polyesters exhibiting a large range in the elastic response causing negligible degradation of the polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48550.     

Thermal degradation of polymers. X. Thermal analysis studies on poly(p-N,N-dimethylaminostyrene) homopolymers and copolymers with styrene in nitrogen

Studies have been made on the effect of the molecular weight of p-N,N-dimethylaminostyrene homopolymers and the composition of its copolymers with styrene on the glass transition temperature. Comparative thermal degradation studies have been made on polystyrene and p-N,N-dimethylaminostyrene polymers by thermal analytical methods (TG, DTA, and DSC). The differences in thermal stability and overall thermal degradation behavior of the two systems are discussed in terms of the differences in their degradation mechanisms.     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

Thermal analysis of polymers and copolymers derived from n-1-alkylitaconamic acids

Poly(N-1-alkylitaconamic acid) (PNAIA) containing ethyl, propyl, butyl, hexyl, octyl, decyl and dodecyl groups and random N-1-alkylitaconamic acid-co-styrene copolymers (NAIA-co-S) of three different compositions were selected and studied by dynamic thermogravimetric analysis (TGA). The thermal stability of homopolymers and copolymers depends on the structure of the NAIA and on the composition of the copolymer. The kinetic analysis of the degradation data shows that the thermal decomposition of the PNAIA can be described by zero order kinetic model. In the case of NAIA-co-S copolymers, the degradation process can be described by two different kinetic orders depending on the copolymer and on the composition. The thermal stability of the PNAIA in general increases as the length of the side chain increases. In the case of copolymers with styrene the relative thermal stability depends clearly on the composition and on the type of substituent in the side chain.     

Enzymatic degradation of thermoresponsive poly(N‐isopropylacrylamide) grafted to carboxymethylcellulose copolymers

The enzymatic degradation of poly(N‐isopropyl acrylamide) (PNIPAM) grafted to carboxymethylcellulose (CMC) copolymers with a cellulasic preparation (Trichoderma viride) was studied. The enzymatic activity of the cellulasic preparation against CMC and the grafted copolymers was determined by the Petterson–Porath method, while their reduced viscosity variation in the presence of the same preparation was also followed. It has been shown that the enzymatic degradation behavior depends on the copolymer composition and the reaction temperature. Reducing sugars analysis showed that the experimental values for the grafted copolymers were higher than the calculated ones. At 50°C, the enzymatic reaction is completed in about 20 min for the copolymers, whereas for CMC it takes more than 40 min. It can be concluded that their enzymatic degradation is facilitated by the presence of the PNIPAM grafts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1383–1386, 2003     

Syntheses and properties of novel copolymers of polycaprolactone and aliphatic polycarbonate based on ketal-protected dihydroxyacetone

The random copolymers of ε-caprolactone (CL) and 2,2-ethylenedioxy propane-1,3-diol carbonate (EOPDC) were synthesized in bulk at 120 °C using Sn(Oct)₂ as a catalyst. The poly(EOPDC-co–CL)s obtained were characterized by FT IR, ¹H NMR, ¹³C NMR, GPC and DSC. The copolymers were obtained with yield of 84.2–97.8 %. The number-average molecular weight of the copolymer is 2.75–7.76 × 10⁴ with a polydispersity of 1.52–1.68. The properties of the copolymer including the enzymatic degradation by Pseudomonas Cepacia lipase and drug-controlled release property were also investigated. The results showed that the copolymers are degradable at physiological conditions, and their degradation rate and release of Tegafur in the copolymers increase with increasing CL content in the copolymers.     

Hydrogels based on N-isopropylacrylamide and methacrylic acid: thermal stability and glass transition behaviour

Summary The thermal stability and glass transition behaviour of crosslinked poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], their random copolymers and sequential interpenetrating polymer networks (IPNs) have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). P(MAA) shows a two-step process of degradation. P(N-iPAAm) shows an unique process of degradation at higher temperature. Copolymers having higher content in N-iPAAm units have a lower thermal stability than their component homopolymers and show an unique degradation process at high temperature. On the contrary, enriched MAA copolymers show better stability but they exhibit two degradation steps at the main degradation region. Sequential IPN samples exhibit a better stability than their component homopolymers and copolymers. The high temperature backbone degradation occurs in only one step, which indicates the formation of a true interpenetrating network. The T _g of the same series of materials has been also measured. A T _g vs composition plot of P(N-iPAAm-co-MAA) copolymers presents a S-shaped curve indicating that structural units interact among them through strong specific interactions. For interpenetrating polymer networks, it seems that only one T _g occurs indicating a good compatibility and interpenetration. Received: 1 December 2001 /Revised version: 12 February 2002/ Accepted: 12 February 2002     

Copolymers of long-side-chain di-n-alkyl itaconates or methyl n-alkyl itaconates with styrene: synthesis, characterization, and thermal properties

Two series of copolymers of styrene with di-n-alkyl itaconates or methyl n-alkyl itaconates with n-alkyl side chains of 12, 14, 16, 18, and 22, using different compositions in the feed have been prepared in bulk via radical at 60 °C with AIBN as initiator. In most of the cases the copolymers were obtained in goods yields, their composition being close to the feed composition and their physical states depending on the composition and the itaconate structure. The copolymers were characterized by FTIR and NMR spectroscopy. The ¹H NMR studies indicate that the copolymers have a mainly random distribution of the monomeric units. The thermal degradation process occurs in one step with decomposition temperatures intermediate between those of polyitaconate and polystyrene. Finally, the alkyl side chains of the itaconate moieties are able to crystallize in a paraffinic phase where the melting temperature and enthalpy increase as the itaconate content and the side chain length rise.     

Structure–property relationship in copolymers of methacrylic acid esters. I. Thermal behavior

This article describes the synthesis and thermal characterization of copolymers of methyl methacrylate (MMA) and alkyl methacrylates. The copolymerization was carried out using different mol fractions (0.05–0.25) of alkyl methacrylates, i.e., octyl methacrylate (OMA)/decyl methacrylate (DMA)/lauryl methacrylate (LMA)/stearyl methacrylate (SMA), in the initial feed at 80°C. The copolymer composition was determined from ¹H-NMR. The thermal stability of the copolymers was investigated by thermogravimetric analysis and pyrolysis gas chromatography. A two/three-step degradation was observed in the copolymer samples. The monomers were the major product of degradation in most of the copolymers except in SMA/MMA copolymers where the product of side-group elimination was also observed. An attempt was also made to determine the yield of the monomers during degradation and then to evaluate the copolymer composition. © 1994 John Wiley & Sons, Inc.     

Preparation and properties of imide–pyrrone copolymers

Two series of copolymers containing imidazopyrrolone (pyrrone) and imide groups were prepared by solution polymerization. Thin films of the copolymers showed a general increase in the tangent modulus and a decrease in elongation with increasing pyrrone content. The copolymers were more resistant to degradation by strong acids and bases than the corresponding polyimides. The thermal stabilities of the copolymers in air improved with increasing imide content, while the thermal stabilities in a vacuum improved with increasing pyrrone content. These copolymers represent a way to combine the desirable properties of both classes of homopolymers.     

Synthesis,characterization, and hydrolytic degradation of copolyesters of 3‐(4‐hydroxyphenyl) propionic acid and p‐hydroxybenzoic acid,vanilic acid,or syringic acid

A series of copolyesters were prepared by a direct polycondensation of 3‐(4‐hydroxyphenyl) propionic acid and p‐hydroxybenzoic acid (HBA), vanilic acid (VA), or syringic acid (SGA) of different composition in pyridine using diphenyl chlorophosphate and lithium bromide as condensing agents. The effects of methoxy substitution in the benzene ring and copolymer composition on the synthesis and thermal properties as well as hydrolytic degradation were examined. The methoxy substitution increased a glass transition temperature and a solubility, while it decreased a crystallinity and a thermal stability. The HBA series copolyesters showed a homogenous nematic phase, while the VA and SGA series copolyestes neither revealed an anisotropic melt nor formed a mobile melt below around 350°C. The hydrolytic degradation of melt‐pressed films was performed in a 5% sodium hydroxide aqueous solution at 40°C to test a biodegradability of the copolyesters. HBA‐50 and HBA‐30 exhibited the much higher degradation rate than HBA‐70, showing that the aliphatic ester linkage was more degradable than aromatic one. The degradation rates of VA‐50 and SGA‐50 were remarkably slower than that of HBA‐50 due to the steric hindrance of the methoxy group in the ortho position. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2474–2481, 2000     

Thermal and photodegradation of vinyl chloride/vinyl bromide copolymers

Vinyl chloride/vinyl bromide (VC/VBr) copolymers have been synthesized by radical copolymerization in bulk. Conversion increases and molecular weight of the copolymers decreases with increasing VBr in the feed. This indicates that VBr is a chain transfer agent in VC/VBr copolymerization systems. In accordance with the lower thermal stability of the vinylbromide homopolymer (PVBr), thermal degradation experiments show that the stability of the copolymers significantly decreases with increasing VBr content. It has been found that the initial rate of dehydrohalogenation is an exponential function of VBr content during thermal degradation of VC/VBr copolymers. In separate experiments, HBr evolved during degradation has been determined by a bromide selective electrode. The initial dehydrobromination rates of VC/VBr copolymers containing higher fractions of VBr are markedly higher than the initial dehydrochlorination rates. This clearly indicates the lower thermal stability of VBr monomer units compared with VC units. UV and visible spectra of degraded VC/VBr copolymers show that the absorption and the average length of polyenes are higher for samples with higher VBr content. Dehydrohalogenation curves obtained during photodegradation of VC/VBr copolymers show a faster initial phase followed by a slower stationary phase. The initial rate of dehydrohalogenation is higher for copolymers containing higher fractions of VBr, whereas these copolymers reach the slower stationary phases at lower extents of dehydrohalogenation.     

Development of degradable poly(ethylene terephthalate)-based nanocomposites with the aid of polylactic acid and graphenic materials: Thermal,thermo-oxidative and hydrolytic degradation characteristics

Poly(ethylene terephthalate)/poly(lactic acid) (PET/PLA) blends with composition of 90/10 and 75/25 (wt %/wt %) along with two types of graphenic materials, namely graphene oxide (GO) and exfoliated graphite (xGnP), were prepared through one-step melt mixing process. The Thermal, thermo-oxidative, and hydrolytic degradation characteristics of the developed degradable PET-based nanocomposites were investigated. Thermal degradation studies by thermogravimetry analysis and melt rheological analysis in N₂ atmosphere, revealed that unlike xGnP, the addition of GO to the blends reduced their thermal stability leading to reduction of viscosity and elasticity of the blends. The behavior was attributed to the role of GO in enhancing the chain scission reactions. In the air atmosphere, the barrier properties of the graphenic materials prevailed. Compared to xGnP, the relatively well-dispersed GO showed better barrier against oxygen and increased the thermo-oxidative stability of the blends. Investigation of the hydrocatalytic degradation of developed systems, at different pH of 2 and 4, over a period of 40 days at 37 °C, showed that the amount of weight loss of the GO-containing nanocomposite systems was higher than that of xGnP. The overall results of thermal, thermo-oxidative, and hydrocatalytic degradation studies confirmed the prominent role of GO in the development of degradable PET-based products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48466.     

Preparation of quinazolone–imide copolymers and their thermal and chemical etching properties

Quinazolone-imide copolymers were prepared by polycondensation of 6,6′-methylenebis(2-methyl-3,1-benzoxazine-4-one) and 3,3′,4,4′-benzophenonetetracarboxlic dianhydride and 4,4′-oxydianiline. Their thermal properties by TGA and their chemical etching properties by the use of the etchant composed of hydrazine hydrate and ethylenediamine were studied. The copolymers obtained had good solubility and excellent heat resistance and gave flexible and tough films. The chemical etching properties were more subject to influence of the polymer composition than the thermal properties were.     

The in vitro and in vivo degradation behavior of poly (trimethylene carbonate-co-ε-caprolactone) implants

The degradation behavior of P(TMC-co-CL) in different compositions was investigated via subcutaneous implantation in vivo. To clarify the role of enzymes in the degradation behavior of the copolymers, hydrolytic and enzymatic degradation were also performed. The mass loss, changes in molecular weight and polydispersity, as well as the variation in composition were monitored with degradation. The changes in thermal and mechanical properties of the specimens were also studied. The results showed that the preferred cleavage of ester bonds resulted in faster degradation in both the hydrolytic and enzymatic cases. Furthermore, the P(TMC-co-CL) had a higher degradation rate in the presence of lipase because it cleaves ester bonds as well as the role of surfactants in the diffusion of the degradation products into water. In vivo, the degradation behavior of the P(TMC-co-CL) depended on their composition—copolymers with a higher TMC content degraded primarily via surface erosion. Bulk degradation was observed for those with a higher CL content. After degradation the mechanical properties and thermal stabilities of the copolymers deteriorated, but the Tm and crystallinity increased via preferred degradation of the amorphous regions. The P(TMC-co-CL) had a tunable degradation rate and remains a promising candidate for clinical subcutaneous implants especially through form-stabilization work.     

Horseradish peroxidase‐mediated in situ forming hydrogels from degradable tyramine‐based poly(amido amine)s

Horseradish peroxidase (HRP)‐mediated crosslinking of poly(amido amine) (PAA) copolymers was successfully applied in the preparation of in situ forming degradable hydrogels under physiological conditions. PAA copolymers containing different amounts of tyramine residues (termed as pAEEOL/TA) could be synthesized through Michael‐type addition between methylenebisacryamide and amine mixture of 2‐(2‐aminoethoxy) ethanol and tyramine (TA). Depending on the amount of TA residue, the HRP, and H₂O₂ concentration, the gelation times could be varied from about 50 to 350 s. The swelling and degradation experiments indicated under physiological conditions the pAEEOL/TA‐based hydrogels are completely degradable within 6–8 days. Rheological analysis revealed that storage modulus of the hydrogels increased from 2500 to 4100 Pa when increasing HRP concentrations. Importantly, pAEEOL/TA copolymers have low cytotoxicity. Moreover, NIH 3T3 (mouse embryonic fibroblast) cells exposed in the degradation products of pAEEOL/TA‐based hydrogels retained high cell viability, implying that the hydrogels are cyto‐biocompatible. In vitro release of methylene blue and IgG protein from pAEEOL/TA‐based hydrogels could be effectively sustained by encapsulation of the drug in the hydrogels. The results indicate that HRP‐crosslinked, degradable pAEEOL/TA‐based hydrogels are promising for biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal behavior of poly(dimethyl itaconate) and poly(di‐n‐butyl itaconate) copolymerized with methyl methacrylate

The thermal degradation behavior of random copolymers of dimethyl itaconate and di‐n‐butyl itaconate with methyl methacrylate was studied. The thennal stability of copolymers depends on the structure of the di‐n‐alkyl itaconate comonomer, and on the copolymer composition. The relative thermal stability increases with the methyl methacrylate copolymer molar fraction, following a trend similar to the glass transition temperature variation. The activation energy was obtained by using MacCallum and Tanner's approach. In addition, the thermal degradation of homopolymers was evaluated in inert atmosphere as well as in thermo‐oxidative conditions, presenting different behaviors.     

Studies on a dicyanate containing four phenylene rings and polycyanurate copolymers. 3. Application of mathematical models to determine the kinetics of the thermal degradation processes

Selected copolymers of bis-4-(4-cyanatophenoxy)phenyl sulphone with a commercial dicyanate, 2,2-bis(4-cyanatophenyl)propane are analysed using thermogravimetry to examine the processes of thermal degradation. Kinetic treatment of the data from these thermal analyses yields three Arrhenius equations for each monomer individually. The kinetics are consistent with a three-stage degradation mechanism, but the total kinetics of the copolymers cannot be derived simply from the sum of the constituent parts added together in proportion to their concentration. Each copolymer reacts slightly differently and must therefore be treated individually.