聚乳酸/聚丁二酸丁二醇酯嵌段共聚物的合成与表征

以丁二酸和1,4-丁二醇为原料,采用熔融缩聚法合成了聚丁二酸丁二醇酯(PBS)预聚物,再与L-丙交酯(L-LA)开环共聚,合成聚乳酸/聚丁二酸丁二醇酯嵌段共聚物(PLLA-co-PBS)。研究了共聚物的结构、热性能、结晶性能和亲水性。结果表明,PBS与L-LA开环共聚生成了PLLA-co-PBS嵌段共聚物;PLLA-co-PBS嵌段共聚物经两个阶段的热分解,且PBS链段的引入提高了聚合物的热稳定性;随着PBS引入量的增加,聚合物的结晶性能,亲水性能都有一定的提高。     

生物降解聚丁二酸丁二醇酯／聚乙二醇嵌段共聚物的合成及表征

以2，4-甲苯二异氰酸酯（TDI）为偶联剂，将端羟基聚丁二酸丁二醇酯预聚物（PBs）与低相对分子质量聚乙二醇（PEG）进行多嵌段共聚，得到PBS／PEG多嵌段共聚物。采用FT-IR、^1H—NMR等方法对产物进行结构表征，同时研究物料配比和偶联剂TDI的用量对共聚物性能的影响及共聚物的吸水率和水解降解行为等。结果表明，PEG的引入使得材料的亲水性显著改善，共聚物的降解速率较纯PBS有大幅度提高。     

枝化聚丁二酸丁二醇酯共聚物的合成及结晶性能研究

采用丁二酸(SA)、1,4-丁二醇(BDO)及枝化单体正丁基缩水甘油醚(BGE)合成了不同枝化度的枝化聚丁二酸丁二醇酯(PBS)共聚物,采用核磁共振仪、X射线衍射仪、差示扫描量热仪以及偏光显微镜对枝化共聚物的化学组成及结晶性能进行了表征。结果表明,枝化单元的引入没有改变聚合物的晶型,但显著改变了其热力学性能,枝化PBS共聚物的熔点(Tm)、结晶度(Xc)均随枝化单体含量的增加逐渐降低;相比纯PBS,枝化PBS共聚物的Avrami指数n降低;高枝化度对结晶形貌,特别是环带的形貌有较大影响。     

电子束辐照交联多接枝共聚物与嵌段双接枝共聚物热塑性弹性体

热塑性弹性体（TPE）由弹性和非弹性的链段共聚而成,是一类重要的聚合物材料。选择合理的分子结构、单体、共聚单元质量分数被认为是优化该类聚合物弹性性能的关键因素。最早的热塑性弹性体是一个弹性体嵌段两端被两个硬嵌段所限制的聚合物。在过去的10年中,新的合成技术应用于合成各种具有精确分子结构设计的接枝共聚物,该项技术的成功开发,使得聚合物主链和侧链的分子量,侧链的分布指数,可接枝点数量,     

PLA/PBAu嵌段共聚物合成工艺优化及降解性能

以端羟基聚乳酸（PLA）、聚己二酸-丁二醇-尿素（PBAu）为预聚物,六亚甲基二异氰酸酯（HDI）为扩链剂,制备出一种新型PLA/PBAu嵌段共聚物。研究了扩链剂用量、扩链温度以及催化剂用量对PLA/PBAu嵌段共聚物分子量的影响,确定了合成PLA/PBAu嵌段共聚物的最佳工艺条件。采用核磁共振、凝胶渗透色谱、差示扫描量热仪、扫描电镜等对共聚物薄膜结构及性能进行表征。结果表明：成功合成了PLA/PBAu嵌段共聚物,分子量可达10×10⁴,玻璃化转变温度约为41℃;并且随着PBAu含量的增加,共聚物的结晶度逐渐增加。以NaOH溶液为模拟液进行加速降解实验发现,当PBAu含量为30%时,可以显著提高嵌段共聚物的降解速率,并且通过调节PLA、PBAu预聚物的含量,可以控制嵌段共聚物的降解速率。     

脂肪族聚丁二酸丁二醇-聚乙二醇嵌段共聚物的制备及性能研究

采用熔融缩聚法以钛酸四丁酯为催化剂,使单体发生酯交换反应,成功制备了一系列以聚乙二醇(PEG)为亲水软段,以聚丁二酸丁二醇酯(PBS)为硬段的嵌段共聚物,采用1H-NMR确定了共聚物的结构组成;采用DSC、吸水性测试及水解降解试验对嵌段共聚物性能表征,结果表明共聚物中两种链段的含量与原料投料比一致,具有可调控性。由于PEG的引入,使共聚物结晶性下降,亲水性和降解性得到显著改善。     

PBS不同化学结构共聚物的性能

采用改变原料的组分合成不同化学结构的聚丁二酸丁二醇酯(PBS)改性共聚物:聚丁二酸丁二醇/己二酸丁二醇酯(PBS-co-BA)、聚丁二酸丁二醇酯/聚丁二酸乙二醇酯(PBS-co-ES)、聚丁二酸丁二醇酯/聚丁二酸己二醇酯(PBS-co-HS),利用FT-IR和1H-NMR表征共聚物的化学结构,并对共聚物的结构与物理性能、降解性能的关系进行对比.研究结果表明:所有共聚物的结晶度、熔点较其均聚物有所降低;但所有共聚物的断裂伸长率都有所提高.热分析结果表明:PBS-co-HS热性能有所提高,PBS-co-BA和PBS-co-ES有所下降.堆肥降解实验表明:所有共聚物的降解性都比均聚物有显著提高,其降解速度大小顺序为:PBS-co-BA>PBS-co-HS>PBS-co-ES>PBS,PBS-co-HS是综合性能最优良的材料.     

生物可降解共聚物PBST和PBS的结构与结晶性能

利用核磁共振氢谱和广角X射线衍射法研究了生物可降解共聚物聚对苯二甲酸-共-丁二酸丁二醇酯(PBST)的结构及结晶性能,并与聚丁二酸丁二醇酯(PBS)进行比较。结果表明:PBST为无规共聚物,其晶体结构为三斜晶系,PBS为均聚物,为单斜晶系,PBST的结晶度和结晶尺寸均比PBS的小。     

聚乙二醇嵌段长碳链二酸共聚物的合成与酶降解研究

采用长碳链癸二酸代替丁二酸与丁二醇以及不同含量的相对分子质量为200的聚乙二醇(PEG)嵌段共聚,得到了聚癸二酸丁二醇酯聚乙二醇嵌段共聚物(PBSe-PEG),并采用核磁共振波谱仪、凝胶渗透色谱仪、差示扫描量分析仪、热重分析仪、广角X射线衍射仪等分析手段表征了嵌段共聚物的结构和性能,并且研究了固定化南极假丝酵母菌脂肪酶(简称脂肪酶N435)对PBSe-PEG的降解性。结果表明,几种PBSe-PEG是预期产物,其数均相对分子质量在5×104左右;PBSe-PEG与纯PBSe相比晶型结构相似;随着PEG含量增加,PBSe-PEG的熔融温度（Tm）和结晶温度（Tc）逐渐下降;相比PBS,脂肪酶N435对PBSe-PEG具有更好的降解性。     

生物降解材料在水环境中降解性能的研究进展

综述了目前典型生物降解材料在水环境中降解性能的研究现状,详细介绍了聚乳酸（PLA）高分子材料（PLA、PLA共聚物、PLA复合材料等）、聚羟基烷酸酯（PHA）、聚己内酯（PCL）、聚丁二酸丁二醇酯（PBS）、聚（己二酸丁二醇酯?对苯二甲酸乙二醇酯）（PBAT）和CO₂共聚物等在不同水环境中的降解性能;最后总结了生物降解材料未来需要关注的问题和发展方向。     

Synthesis and thermal studies of block copolymers from NR and MDI‐based polyurethanes

Five series of block copolymers based on natural rubber and polyurethane were prepared from hydroxyl terminated liquid natural rubber (HTNR) and polyurethane (PU) formed by the reaction of diphenyl methane—4,4′—diisocyanate (MDI) with a chain extender diol, viz., ethylene glycol (EG)/propylene glycol (PG)/1,4‐butane diol (1,4‐BDO)/1,3‐butane diol (1,3‐BDO)/bisphenol A (BPA), by solution polymerization. Structural characterization of the block copolymers was done by infrared (IR) analysis. Thermal studies and kinetic analysis on thermal degradation of the block copolymers were undertaken with the view of characterizing them. Energy of activation and entropy change for the degradation were determined and a probable mechanism for the solid state degradation was suggested which corresponds to a three dimensional diffusion mechanism. DSC analysis has been used for the study of microphase separation in the block copolymers. Thermal transition of the hard segment significantly varies with the extender diol which highlights the effect of extender diol structure on the chain stiffening mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Cationic polymerization of α-methyl styrene from polydienes. II. Tensile properties of poly(butadiene-g-α-methyl styrene) and poly(styrene-b-butadiene-g-α-methyl styrene) copolymers

Tensile properties of poly(butadiene-g-α-methyl styrene) copolymers have been investigated on molded samples. These graft copolymers show thermoplastic elastomer behavior because of their graft copolymer structure. Both modulus and strength increase with increasing α-methyl styrene content and tensile strength is highest at the 45–50% by weight α-methyl styrene level. Tensile strength at elevated test temperatures is considerably higher for these poly(butadiene-g-α-methyl styrene) copolymers than for styrene-butadiene-styrene triblock polymers. This is attributed to the higher glass transition temperature for poly(α-methyl styrene) segments compared to polystyrene segments. The oil acceptance of these graft copolymers appears to depend on the number of loose polybutadiene chain ends. Thus, the tensile strength of oil-extended poly(butadiene-g-α-methyl styrene) copolymers was considerably lower than oil-extended poly(styrene-b-butadiene-g-α-methyl styrene) copolymers even though both copolymers contained equal hard segment contents.     

Ring-opening polymerization of a macrocyclic lactone monomer isolated from oligomeric byproducts of poly(butylene succinate) (PBS): An efficient route to high-molecular-weight PBS and block copolymers of PBS

A macrocyclic lactone (BSD) consisting of butylene succinate dimer was successfully isolated from oligomeric byproducts of poly(butylene succinate) (PBS) prepared by the polycondensation method. BSD was subjected to ring-opening polymerization (ROP) with tin octoate as the catalyst to obtain PBS. Its number-average molecular weight was found to reach about 9.5 × 10^４ Da, being much higher than that of the PBS sample obtained by direct melt polycondensation. When the ROP of BSD was performed in the presence of polyethylene glycol (PEG) as the macro-initiators, triblock (PBS-PEG-PBS) and diblock (PEG-PBS) copolymers were obtained.     

Tri-block copolymers with mono-disperse crystallizable diamide segments: Synthesis, analysis and rheological properties

Tri-block copolymers with polyether mid-segments and mono-disperse amide end segments were synthesized, analyzed and some properties studied. The end segment was an aromatic diamide (diaramide, TΦB). The polyether mid-segment was a difunctional poly(tetramethylene oxide) (PTMO, 1000 and 2900 g/mol). In order to increase the soft segment (SS) length, PTMOs were extended with terephthalic groups. The length of the mid-soft segment was varied from 1000 to 20,000 and thereby the concentration of the hard end segment changed from 22 to 3 wt.%. The molecular weight of the tri-block copolymers was determined by NMR and inherent viscosity measurements. The crystallinity of the hard segment was studied by IR and DSC measurements. Temperature modulated IR was carried out to explore the change in crystallinity with temperature. The morphology was investigated by AFM analysis and the thermo-mechanical properties by DMA, whereas the melt rheological behaviour was analyzed by a plate–plate method. The results of the tri-block copolymer were compared with those of a similar multi-block copolymer. The glass transition of the soft phase was low and the melting temperature of the diamide end blocks was high. The crystallinity of the hard end segments in the tri-block was found to be very high (>95%) and remained high until melting. The AFM picture showed crystalline ribbons with a high aspect ratio. Also the modulus at room temperature was relatively high, particularly at low contents of hard end segment. The melt rheological behaviour of a low molecular weight tri-block copolymer revealed a low melt viscosity at high shear rates, and a high viscosity at low shear rates. Moreover, a gelling of the melt was observed with decreasing frequency and this was probably due to agglomeration of the end segments.     

Synthesis,characterization and biocompatibility of novel biodegradable poly[((R)‐3‐hydroxybutyrate)‐block‐(D,L‐lactide)‐block‐(ε‐caprolactone)] triblock copolymers

BACKGROUND: Biodegradable block copolymers have attracted particular attention in both fundamental and applied research because of their unique chain architecture, biodegradability and biocompatibility. Hence, biodegradable poly[((R )‐3 ‐hydroxybutyrate)‐block‐(D ,L ‐lactide)‐block‐(ε‐caprolactone)] (PHB‐PLA‐PCL) triblock copolymers were synthesized, characterized and evaluated for their biocompatibility. RESULTS: The results from nuclear magnetic resonance spectroscopy, gel permeation chromatography and thermogravimetric analysis showed that the novel triblock copolymers were successfully synthesized. Differential scanning calorimetry and wide‐angle X‐ray diffraction showed that the crystallinity of PHB in the copolymers decreased compared with methyl‐PHB (LMPHB) oligomer precursor. Blood compatibility experiments showed that the blood coagulation time became longer accompanied by a reduced number of platelets adhering to films of the copolymers with decreasing PHB content in the triblocks. Murine osteoblast MC3T3‐E1 cells cultured on the triblock copolymer films spread and proliferated significantly better compared with their growth on homopolymers of PHB, PLA and PCL, respectively. CONCLUSION: For the first time, PHB‐PLA‐PCL triblock copolymers were synthesized using low molecular weight LMPHB oligomer as the macroinitiator through ring‐opening polymerization with D ,L ‐lactide and ε‐caprolactone. The triblock copolymers exhibited flexible properties with good biocompatibility; they could be developed into promising biomedical materials for in vivo applications. Copyright © 2008 Society of Chemical Industry     

Amorphous state transitions in butadiene–acrylonitrile copolymers

Differential thermal analysis, creep measurements, and gas permeation rates are used to confirm the existence of a transition zone in three butadiene acrylonitrile copolymers in a temperature region that starts at roughly 15° to 25°C above the main glass transition temperatures of the copolymers and extends over a broad temperature range. The change appears to be slightly endothermic and softens the copolymers upon heating. It is speculated that the copolymers are in a mesomorphic state above their main glass temperature in which there is either a degree of ordering or a low-grade crystallinity of polybutadiene units along the copolymer chains. It is not until the copolymers are 50° to 75°C above their main glass temperature that they become truly amorphous.     

Synthesis,characterization and properties of biodegradable poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyesters

BACKGROUND: To obtain a biodegradable thermoplastic elastomer, a series of poly(ester‐ether)s based on poly(butylene succinate) (PBS) and poly(propylene glycol) (PPG), with various mass fractions and molecular weights of PPG, were synthesized through melt polycondensation. RESULTS: The copolyesters were characterized using ¹H NMR, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, mechanical testing and enzymatic degradation. The results indicated that poly(ester‐ether)s with high molecular weights were successfully synthesized. The composition of the copolyesters agreed very well with the feed ratio. With increasing content of the soft PPG segment, the glass transition temperature decreased gradually while the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased. Mechanical testing demonstrated that the toughness of PBS was improved significantly. The elongation at break of the copolyesters was 2–5 times that of the original PBS. Most of the poly(ester‐ether) specimens were so flexible that they were not broken in Izod impact experiments. At the same time, the enzymatic degradation rate of PBS was enhanced. Also, the difference in molecular weight of PPG led to properties being changed to some extent among the copolyesters. CONCLUSION: The synthesized poly(ester‐ether)s having excellent flexibility and biodegradability extend the application of PBS into the areas where biodegradable thermoplastic elastomers are needed. Copyright © 2009 Society of Chemical Industry     

Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide). Part 4. Influence of the extender

Copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments, uniform crystallisable tetra-amide units (T6T6T, 6-15 wt%) and different diols (C2-C36, polytetramethylene oxide) as an extender were synthesised. The telechelic PPE segment was end-functionalised with terephthalic ester groups and had a molecular weight of 3100 g/mol. The coupling between the PPE segment and the T6T6T unit was made with diols. The influence of the length and flexibility of the diol-extender and the concentration of the T6T6T units were studied on the thermal (DSC) and thermal-mechanical (DMA) properties of the copolymers. A crystalline T6T6T phase in the copolymers was evident from 9 wt% onwards. The length of diol extender had an effect on the glass transition temperature of the PPE phase, the crystallinity of the T6T6T segments and modulus above the glass transition temperature. With ethylene glycol the T_g of the copolymer was high but the crystallinity of the T6T6T rather low. With dodecanediol or hexanediol as an extender the T_gs of the PPE phase were somewhat lower, but the crystallinities of the T6T6T segments higher. With C36 and polytetramethylene oxide diols, the T_g were strongly decreased and broad and the modulus above the glass transition temperature not so high.