A series of non-isocyanate linear high molecular weight poly(ester urethane)s(PETUs)were prepared through an environmentallyfriendly route based on dimethyl carbonate,1,6-hexanediol and 1,6-hexanediamine.In this route,the polyurethane diol was first prepared by the reaction between bis-1,6-hexamethylencarbamate(BHC)and 1,6-hexanediol.A series of polyester soft segments of polyurethane have been synthesized from the polycondensation of adipic acid and different diols,including butanediol,hexanediol,octanediol and decanediol.The subsequent polycondensation of polyurethane diol and polyester diol led to linear PETUs.The resultant polymers were characterized by GPC,FTIR,1H-NMR,13C-NMR,DSC,WAXD,TGA and tensile test.The results indicated that PETUs possess weight-average molecular weights higher than 1×105 and the tensile strength as high as 10 MPa.The thermal properties,crystallization behavior,microphase separation behavior and morphology were studied by DSC and AFM,and the results indicated that the degree of phase separation was affected by two factors,the crystallization and hydrogen bonding interaction between soft segment and hard segment. 相似文献
Biodegradable polyurethane elastomers with potential for applications in medical implants with tunable degradation rate and physical properties were synthesized from reaction of epoxy terminated polyurethanes (EUP) with 1,6-hexamethylene diamine (HMDA) as curing agent. Poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as well as 1,6-hexamethylene diisocyanate (HDI) were used for preparation of isocyanate terminated polyurethanes which were subsequently blocked with glycidol to prepare EUPs. All materials were characterized by conventional methods, and their properties were studied fully. Results showed that elastomers based on PEG exhibit superior degradation rate and inferior mechanical properties in comparison to elastomers based on PCL. Optimum degradation rate and mechanical properties were obtained from elastomers made from mixture of PCL and PEG base EUPs. 相似文献
A series of multiblock poly(ether-ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether-ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl succinate, 1,4-butanediol and α,ω-hydroxyl terminated poly(ethylene oxide) (PEO, = 1000 g/mol) in bulk. The content of soft PEO segments in the polymer chains was varied from about 10 to 50 mass%. The effect of the introduction of the soft PEO segments on the structure, thermal and physical properties, as well as on the biodegradation properties was investigated. The composition and structure of these aliphatic segmented copolyesters were determined by 1H NMR spectroscopy. The molecular weights of the polyesters were verified by gel permeation chromatography (GPC), as well as by viscometry of dilute solutions and polymer melts. The thermal properties were investigated using differential scanning calorimetry (DSC). The degree of crystallinity was determined by means of DSC and wide-angle X-ray scattering. A depression of melting temperature and a reduction of crystallinity of the hard segments with increasing content of PEO segments were observed. Biodegradation of the synthesized copolyesters, estimated in enzymatic degradation tests in phosphate buffer solution with Candida rugosa lipase at 37 °C was compared with hydrolytic degradation in the buffer solution. The weight losses of the samples were in the range from 2 to 10 mass%. GPC analysis confirmed that there were significant changes in molecular weight of copolyesters with higher content of PEO segments, up to 40% of initial values. This leads to conclusion that degradation mechanism of the poly(ether-ester)s based on PEO segments occurs through bulk degradation in addition to surface erosion. 相似文献
IntroductionDimethyl carbonate(DMC) is known to be a novelbuilding block in organic synthesis. As an environmen-tally benign compound and a unique intermediate,DMC has attracted much attention[1,2]. Among the va-rious methods for synthesizing DMC, the tra… 相似文献
A series of novel poly(trimethylene terephthalate)-block-poly(tetramethylene oxide) (PTT--PTMO) segmented block copolymers were synthesised by transesterification in the melt of dimethyl terephthalate, 1,3-propanediol and poly(tetramethylene oxide) glycol (PTMO, 1000 g/mol). A range of multiblock copolymers were synthesized, with flexible PTMO segments contents varying from 20 to 80 wt%. The novel poly(ether-block-ester)s were characterized by using viscometry, hardness measurements, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile properties. 相似文献
Biodegradable elastomers represent a useful class of biomaterials. In this paper, a novel biodegradable elastomer, poly(PEG-co-CA) (PEC), was synthesized by condensation of poly(ethylene glycol) (PEG) and citric acid (CA) under atmospheric pressure without any catalyst. We first synthesized a pre-polymer by carrying out a controlled condensation reaction between PEG and citric acid, and then post-polymerised and simultaneously cross-linked the pre-polymer in the mould at 120 °C. The pre-polymer was characterized by FT-IR, 1H NMR, 13C NMR, GPC and DSC. A series of polymers were prepared at different post-polymerisation time and different monomer ratios. Measurements on the mechanical properties of PEC testified that the new polymers are elastomers with low hardness and big elongation, and hydrolytic degradation of the polymer films in a buffer of pH 7.4 at 37 °C showed that PEC had excellent degradability (all the films show the weight losses more than 60% after 96 h incubation). The different post-polymerisation time and monomer ratio had strong influence on the degradation rates and mechanical performances. The material is expected to be useful for controlled drug delivery and other biomedical applications. 相似文献
Fluorinated copolymers are well known for their large range of applications. These applications can be improved by grafting or crosslinking of several agents. The mechanism of crosslinking of hexamethylene diamine and 2,4,4-trimethyl-1,6-hexanediamine is well known and occurs in four different steps. To elaborate a film of commercially available poly(VDF-co-HFP) copolymer crosslinked by 2,4,4-trimethyl-1,6-hexanediamine, a step of press cure under air is necessary. Temperature, time and pressure were optimised by regarding the solubility of the press cured films, the mechanical properties, the swelling rate in methyl ethyl ketone, and the degradation of the films. The best temperature, time and pressure for press cure were 150 °C, from 15 to 30 min, and 20 bars, respectively. Other properties of crosslinked poly(VDF-co-HFP) copolymers containing 10 mol.% and 20 mol.% of HFP were characterized. First, all films were insoluble in concentrated HCl. Secondly, swelling rates of different amounts of diamine crosslinked copolymers were measured in ethylene carbonate/dimethyl carbonate and in methyl ethyl ketone; it was proved that the higher the molar percentage of diamine, the higher the crosslinking density, so the lower the swelling rate. Concerning thermal properties, glass transition temperature mainly increased when the amount of diamine increased. Thermal stability measurements showed a higher decomposition temperature when the percentage of diamine was very low (5 mol.%). Finally, mechanical properties were measured by dynamic mechanical analysis; the storage tensile modulus (E′) of a diamine crosslinked Kynar® copolymer versus temperature exhibited a high drop because Kynar® was a highly amorphous copolymer. Moreover, the higher the amount of diamine, the higher the rubbery modulus. 相似文献
Two new diacid monomers, 2,2′-sulfide bis(4-methyl phenoxy acetic acid) and 2,2′-sulfoxide bis(4-methyl phenoxy acetic acid) were successfully synthesized by refluxing the 2,2′-sulfide bis(4-methyl phenol) and 2,2′-sulfoxide bis(4-methyl phenol) with chloroacetonitrile in the presence of potassium carbonate, and subsequent basic reduction. Two novel series of poly(sulfide-ether-amide)s and poly(sulfoxide-ether-amide)s with aliphatic units in the main chain were prepared from diacids with various diamines.The polyamides were obtained in quantitative yields and their inherent viscosities were in the range of 0.43-0.89 dl g−1 at a concentration of 0.5 g dl−1 in N,N-dimethylacetamide (DMAc) solvent at 25 °C. They showed good thermal stability. The temperature for 10% weight loss in argon atmosphere was in the range of 350-415 °C. The polymers showed glass transition temperatures between 228 and 261 °C. Almost all of the polyamides were readily soluble in a variety of polar solvents such as N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). 相似文献
The hydrolytic degradation of Monosyn™, a segmented copolymer derived from glycolide, trimethylene carbonate and ε-caprolactone, has been evaluated in buffered aqueous media at different pH and temperature. Degradation processes have been followed by considering mass loss and molecular weight profiles as well as the changes on 1H NMR and FTIR spectra, morphology and both calorimetric and mechanical properties during exposure to the selected media and temperature. 相似文献
Segmented poly(ester-urethanes) (PU) elastomers based on poly(ethylene diethylene adipate)diols as a soft segment and aromatic diisocyanates in the hard segment were synthesized by a conventional method. The precipitated PU elastomers films have been degraded after a limited exposure to free radical agents. An increase of the ratio of radical agents had an increase in the hard segment content which was associated with increased hard microdomain crystallinity, hardness and improvement in mechanical properties. It is suggested that the superior mechanical performance may be related to a interconnecting hard microdomain texture by a radical cross-linking process. The present study attempts to correlate the physical-mechanical properties of the precipitated PU films with the concentration of the free radical agents. In all cases, the effect of free radical cross-linking was to increase the ultimate tensile strain. 相似文献
The direct enzymatic synthesis of a cyclic trimethylene carbonate (1,3‐dioxane‐2‐one) monomer with/without a methyl substituent was carried out using dimethyl or diethyl carbonate and 1,3‐diol with the objective of producing aliphatic poly(trimethylene carbonate), a typical biodegradable synthetic plastic. The lipase‐catalyzed condensation of dimethyl or diethyl carbonate with aliphatic 1,3‐diols using immobilized Candida antarctica lipase (lipase CA) in an organic solvent at 70 °C afforded the corresponding methyl‐substituted and unsubstituted cyclic trimethylene carbonates. The cyclic trimethylene carbonates obtained by the reaction of dimethyl or diethyl carbonates with 1,3‐propanediol and 2‐methyl‐1,3‐propanediol were polymerized by lipase to produce the corresponding polycarbonates.
Total TMC yield as a function of the reaction time. 相似文献
In this work, the feasibility of replacing petroleum-based poly(ethylene terephthalate) (PET) with fully bio-based copolyesters derived from dimethyl 2,5-thiophenedicarboxylate (DMTD), dimethyl 2,5-dimethoxyterephthalate (DMDMT), and polysaccharide-derived 1,6-hexanediol (HDO) was investigated. A systematic study of structure-property relationship revealed that the properties of these poly(thiophene–aromatic) copolyesters (PHS(20–90)) can be tailored by varying the ratio of diester monomers in the reaction, whereby an increase in DMTD content noticeably shortened the reaction time in the transesterification step due to its higher reactivity as compared with DMDMT. The copolyesters had weight-average molar masses (Mw) between 27,500 and 38,800 g/mol, and dispersity Đ of 2.0–2.5. The different polarity and stability of heterocyclic DMTD provided an efficient mean to tailor the crystallization ability of the copolyesters, which in turn affected the thermal and mechanical performance. The glass transition temperature (Tg) could be tuned from 70–100 °C, while the tensile strength was in a range of 23–80 MPa. The obtained results confirmed that the co-monomers were successfully inserted into the copolyester chains. As compared with commercial poly(ethylene terephthalate), the copolyesters displayed not only enhanced susceptibility to hydrolysis, but also appreciable biodegradability by lipases, with weight losses of up to 16% by weight after 28 weeks of incubation. 相似文献
Isomeric homopolymers and random copolyesters based on sebacic acid and isomeric hexanediols were synthesized by condensation techniques and characterized by NMR, GPC, intrinsic viscosity, and DSC. Among the homopolymers, only the polyester derived from the linear 1,6-hexanediol was found to be crystalline. Typical melting points were 65–70°C, depending on molecular weight, and a Tg of ?62°C was measured on a high molecular weight sample. Other isomeric homopolymers derived from the branched diols 2-methyl-2-ethyl-1,3-propanediol and 2,5-hexanediol were amorphous tacky fluids with glass temperatures of ?69 and ?66°C, respectively. In the case of the random copolymers, NMR analysis was particularly useful in determining the copolymer composition or the diol isomer ratio. DSC data indicated that all the random copolymers containing the linear 1,6-diol were crystallizable and their melting points depended on copolymer composition. The heat of fusion per repeat unit of poly(hexamethylene sebacate) was found to be 32 cal/g from measurements of the molecular weight dependence of the melting point. 相似文献
Series of PTT-b-PEO copolymers with different composition of rigid PTT and PEO flexible segments were synthesized from dimethyl terephthalate (DMT), 1,3-propanediol (PDO), poly(ethylene glycol) (PEG, Mn= 1000 g/mol) in a two stage process involving transesterification and polycondensation in the melt. The weight fraction of flexible segments was varied between 20 and 70 wt%. The molecular structure of synthesized copolymers was confirmed by 1H NMR and 13C NMR spectroscopy. The superstructure of these polymers was characterized by DSC, DMTA, WAXS and SAXS measurements. It was observed that domains of three types can exist in PTT-b-PEOT copolymers: semi-crystalline PTT, amorphous PEO rich phase (amorphous PEO/PTT blended phase) and semi-crystalline PEO phase. Semi-crystalline PEO phase was observed only at temperature below 0 °C for sample containing the highest concentration of PEO segment. The phase structure, thermal and mechanical properties are effected by copolymer composition. The copolymers containing 30÷70 wt% of PEO segment posses good thermoplastic elastomers properties with high thermal stability. Hardness and tensile strength rise with increase of PTT content in copolymers. 相似文献