接枝共聚物聚苯乙烯－g－聚氧乙烯的微相分离形态研究

 本文利用透射电子显微镜技术，以两性接校共聚物聚苯乙烯－ｇ－聚氧乙烯为研究对象，研究了接枝共聚物的微相分离形态结构，发现聚苯乙烯－ｇ－聚氧乙烯能形成微相分离结构，微区的形状和尺寸与共聚物的组成和侧链长度有关．文中还讨论了嵌段共聚物和接枝共聚物在形成微相分离结构时的共性和个性．     

接枝共聚物聚苯乙烯－g－聚氧乙烯的微相分离形态研究

本文利用透射电子显微镜技术，以两性接校共聚物聚苯乙烯－ｇ－聚氧乙烯为研究对象，研究了接枝共聚物的微相分离形态结构，发现聚苯乙烯－ｇ－聚氧乙烯能形成微相分离结构，微区的形状和尺寸与共聚物的组成和侧链长度有关．文中还讨论了嵌段共聚物和接枝共聚物在形成微相分离结构时的共性和个性．     

聚氨酯一聚丙烯酸酯共聚乳液的合成研究

以甲基丙烯酸β－羟乙酯封端的聚氨酯大分子单体与丙烯酸酯类单体进行乳液共聚，合成了以聚丙烯酸酯（PA）为主链、聚氨酯（PU）为侧链的接枝共聚物（PA－g－PU）乳液，用IR光谱和^1H NMR光谱对该聚氨酯大分子单体及PA－g－PU接枝共聚物进行了表征，并对影响聚氨酯－聚丙烯酸酯共聚合的因素进行了探讨。结果表明：聚氨酯大分子单体的加入对乳液聚合的速率造成较大的影响。该体系的表观活化自由能为99.39KJ/mol,Rp∝[I]^0.87,Rp∝[S]^0.12。     

通过正离子聚合原位制备壳聚糖-g-聚四氢呋喃接枝共聚物/银纳米复合材料

采用活性正离子开环聚合方法合成聚四氢呋喃(PTHF)活性链,再通过"grafting onto"方式接枝到壳聚糖(CS)刚性主链上,原位制备壳聚糖-g-聚四氢呋喃接枝共聚物/银纳米复合材料.采用FTIR、1H-NMR和XPS分别表征该接枝共聚物化学结构,采用AFM、TEM、HR-TEM、POM、SEM、TGA和UV研究复合材料的Ag含量、微观结构与形态,并研究该复合材料的载药/释药性和抗菌性能.结果表明:通过上述方法可以原位制备出壳聚糖-g-聚四氢呋喃接枝共聚物/银(CS-g-PTHF/Ag)纳米复合材料,PTHF支链的平均分子量为1400~2600,以1000个氨基葡萄糖环为整体计算接枝链PTHF的平均支链数目为4~21,纳米Ag的质量含量为2.2%~5.7%.所制备的CS-g-PTHF接枝共聚物形成明显的微观相分离结构,主链CS的结晶性随着侧链PTHF接枝数目增大而受到限制,结晶形态发生变化;CS-gPTHF接枝共聚物可作为药物载体,载药率在53%~80%之间,载药微球的尺寸随侧链PTHF接枝数目增大而减小;CS-g-PTHF接枝共聚物载药微球具有一定的p H敏感性,CS-g6-PTHF1.4k在p H=6.0的弱酸性环境中释放速率快,25 h时药物释放完全.CS-g7-PTHF2.6k/Ag-5.7纳米复合材料表现出良好的抗菌性,对于抗大肠杆菌,抑菌圈直径为13.0 mm,对于抗黑曲霉,抑菌圈直径为10.5 mm.所制备的CS-gPTHF/Ag纳米复合材料结合了壳聚糖良好的生物相容性、聚四氢呋喃优异的抗湿强度与柔韧性以及纳米银优良的抗菌性,在生物医学领域具有潜在应用前景.     

聚氨酯弹性体的相区相容性和阻尼性能研究

合成了一系列含有不同软段的聚氨酯嵌段共聚物及接枝共聚物,并测试了其动态力学性能,结果表明,聚氨酯共聚物的相容性与大分子的链结构有关,接枝链的存在对聚氨酯嵌优共聚物相空性和阻尼性能有很大影响。     

聚甲基丙烯酸酯改性聚氨酯光固化水性体系研究

水性涂料;聚甲基丙烯酸酯改性聚氨酯光固化水性体系研究;接枝共聚物;聚氨酯丙烯酸酯;丙烯酸酯共聚物     

甲壳素和壳聚糖的接枝共聚改性

天然高分子甲壳素、壳聚糖由于分子链上大量存在的反应性官能团 ,易于通过自由基引发与乙烯基单体接枝共聚 ,也可与其它高分子链偶合制得接枝共聚物。通过接枝共聚改性 ,可以赋予甲壳素和壳聚糖以某些新的性能 ,扩大了其应用范围。本文对甲壳素、壳聚糖的接枝共聚改性反应进展、机理以及产物的性能等进行了介绍     

淀粉与聚丁二酸己二醇酯的反应及其生物降解性研究

合成了一种新型的完全生物降解型材料－淀粉－聚丁己二醇酯共聚物，对影响聚丁二酸己二醇酯的分子量及淀粉与聚丁二酸己二醇酯反应接枝率的主要因素进行了研究，当聚丁二酸己二醇酯酰氯化物与淀粉投料重量比为４：１时，聚酯的接枝率达到３８．２０％，接枝共聚物用枯草芽孢杆菌和金黄色葡萄球菌降解４０ｄ，其失重率达８９．６０％，在土壤中堆埋９０ｄ，接枝共聚物基本完全被降解。     

聚甲基丙烯酸-聚酯接枝共聚物

本工作合成了含有聚甲基丙烯酸和各种聚酯(聚ω-羟基庚酸酯,聚ω-羟基壬酸酯或聚ω-羟基十一酸酯)的接枝共聚物。结果表明,接枝共聚物的产率和反应速率与原料的比例以及所用聚酯结构单位中—CH_2—数目有关。 所得接枝共聚物只溶于含有极性和非极性的溶剂(例如苯甲醇)中,它在单一的极性或非极性溶剂中的溶胀度与接枝共聚物中聚甲基丙烯酸主链和聚酯枝链的比值以及所用聚酯分子结构有关。 不同聚酯枝链的结构和含量使所得的接枝共聚物具有不同的结晶度。结晶形的接枝共聚物有可能形成球晶。 接枝共聚物在高于原来聚酯的熔点和高于ΠMAK的分解温度以上的宽广温度范围内(220—250℃)出现高弹态。     

壳聚糖-聚丙烯酰胺接枝共聚物接枝率的测定

根据溶液的折光指数增量与溶液的组成间存在定量关系的原理提出了一种测定接枝聚合物接枝率的新方法, 并用此方法测定了壳聚糖-聚丙烯酰胺接枝共聚物的接枝率. 结果通过元素分析法测定样品中氮元素的百分含量, 以及运用折光指数增量法测定已知比例的壳聚糖与聚丙烯酰胺(PAM)混合物中二者的质量百分比进行佐证. 结果表明, 折光指数增量法测定接枝共聚物的接枝率也是可行的.     

具有电活性苯胺四聚体接枝聚谷氨酸的合成与表征

以N-羟基琥珀酰亚胺(NHS)活化聚L-谷氨酸的羧基并与苯胺四聚体的氨基缩合,得到了以可生物降解的聚谷氨酸为主链,具有电活性的苯胺四聚体为侧链的新型接枝聚合物.用1H-NMR、质谱分析、光谱分析的方法确定了化合物的结构.侧链羧基的存在使聚合物可以溶解于碱性的缓冲溶液中.对聚合物的电化学性质进行了紫外及循环伏安的表征,研究结果表明,接枝后的聚合物具有与苯胺低聚体相似的可逆的氧化还原过程并可被质子酸掺杂,表现出良好的电化学活性.同时,以定量紫外吸收及元素分析的方法分别测定了聚合物的接枝率.实验中通过控制反应的投料比可以使苯胺四聚体的接枝率达到40%以上,并对聚合物的自掺杂现象进行了讨论.     

Physicochemical characterization of polymeric micelles constructed from novel amphiphilic polyphosphazene with poly(N-isopropylacrylamide) and ethyl 4-aminobenzoate as side groups

An amphiphilic graft polyphosphazene (PNIPAm/EAB-PPP) composed of oligo-poly(N-isopropylacrylamide) (PNIPAm) as hydrophilic segments and ethyl 4-aminobenzoate (EAB) as hydrophobic groups was synthesized via ring-opening polymerization and subsequent substitution reaction. The molar ratio of the PNIPAm segment to EAB group was 1.85:0.15. The lower critical solution temperature (LCST) of copolymer was 32.6 degrees C as determined by turbidity method. Micellization behavior of PNIPAm/EAB-PPP in an aqueous phase was characterized by fluorescence technique, 1H NMR, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The critical micelle concentration (CMC) of the graft copolymer in aqueous solution was 0.1mg/ml. The number-averaged particle size of spherical micelles was 80 nm at 25 degrees C with a narrow distribution. TEM also revealed that inter-micellar aggregation was induced in the micelle solution at temperature above LCST of graft copolymer. The thermosensitive PNIPAm/EAB-PPP micelles may be of help to regulate the loading and release of hydrophobic drugs.     

Water-soluble graft copolymers from macromonomer method

Water-soluble graft copolymers of well-defined structure having hydrophobic polymethacrylate branches with different ester groups were prepared by the macromonomer method. Methacrylate macromonomers of controlled molecular weights having a methacryloyloxyl end group were synthesized by radical polymerization of the corresponding monomer in the presence of thioglycolic acid followed by the reaction of glycidyl methacrylate with the terminal carboxyl group. These macromonomers were copolymerized with methacrylic acid and methyl methacrylate to prepare tailor-made graft copolymers composed of a hydrophlic backbone and different kinds of hydrophobic branches, which were characterized by elemental analysis, NMR, and GPC. The viscosities of the aqueous solutions of the sodium salts of these graft copolymers were measured. It was found that the viscosity of the dilute solution of the graft copolymer was remarkably high compared with the corresponding random copolymer irrespective of the ester group in branch segments. Solubilizing behavior of Orange-OT in aqueous solutions of the graft copolymers and the random copolymer were also investigated to study the nature of the hydrophobic domain of the graft copolymers.     

A starlike amphiphilic graft copolymer with hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chains

A well‐defined starlike amphiphilic graft copolymer bearing hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chains was synthesized by successive atom transfer radical polymerization followed by the hydrolysis of poly‐(methoxymethyl acrylate) backbone. A grafting‐from strategy was employed for the synthesis of a graft copolymer with narrow molecular weight distribution. Hydrophobic polystyrene side chains were connected to the backbones through stable C? C bonds. The poly(methoxymethyl acrylate) backbones can be easily hydrolyzed with HCl without affecting the hydrophobic polystyrene side chains. This kind of amphiphilic graft copolymer can form stable sphere micelles in water. The sizes of the micelles were dependent on the ionic strength and pH value. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3687–3697, 2007     

Grafting of polymethyl methacrylate from poly(ethylene-co-vinylacetate) copolymer using atom transfer radical polymerization

Atom transfer radical polymerization was employed for the first time to prepare graft copolymer having by ethylene-vinyl acetate (EVA) copolymer as backbone and poly(methyl methacrylate) (PMMA) as branches. The polymerization of MMA was initiated by EVA carrying chloropropionate groups as macroinitiator, in the presence of copper chloride (CuCl) and bipyridine (bpy) at 80 °C. The macroinitiator was prepared by esterification of partially hydrolyzed EVA with 2-chloropropionyl chloride. Successful graft copolymerizations were performed both in toluene/γ-butyrolactone mixed solvent and in toluene solution, with grafting efficiency of 12% and 6%, respectively. Molecular weight distribution of the PMMA segments around 1.2 has been achieved with pure toluene solution. The ATRP graft copolymerization was supported by an increase of the molecular weight of the graft copolymers, as compared to that of the macroinitiator and also by their monomodal molecular weight distribution.     

Emulsifying effect of graft copolymer for the homopolymer

Precipitation of poly(methyl methacrylate) (PMMA) from dimethyl sulfoxide solution by addition of water as a precipitant was studied in the presence of a well-characterized graft copolymer of poly(vinyl alcohol) (PVA). The graft copolymer which had been prepared by a radiation method and freed from PMMA and PVA homopolymers had one PMMA branch whose length was nearly equal to that of the PVA backbone. Even when such an amount of water was added to PMMA solution as to cause all the PMMA to precipitate from the solution, the precipitation was prevented by the presence of relatively small amounts of the graft copolymer. With decreasing molecular weight of PMMA, the effect of protection became more pronounced. When the precipitation was prevented, the solution was transformed into a stable emulsion. The mechanism of protection against precipitation was discussed on the basis of the results obtained and electron microscopic photographs of the emulsion particles. It was concluded that the particles of the precipitated homopolymer were covered by a monolayer of the graft copolymer, resulting in prevention of coagulation.     

催化链转移聚合制备接枝型两亲共聚物及其溶液性质研究

采用大分子单体法制备接枝型两亲共聚物, 通过表面张力仪、偏光显微镜、旋转流变仪和小角X射线衍射研究了两亲共聚物在水溶液中的聚集行为及其相结构. 首先末端带有可聚合双键的聚甲基丙烯酸叔丁酯大分子单体(PtBMA Macromonomer)通过催化链转移聚合法制备, 所用到的催化链转移剂为二水合双(二氟化硼苯二酮肟)合钴(II) (COPhBF). 然后将所得到的大分子单体与丙烯酸正丁酯(BA)进行自由基共聚得到接枝共聚物PBA-g-PtBMA, PBA-g-PtBMA中PtBMA的侧链部分在酸性条件下定量水解成聚甲基丙烯酸(PMAA)并用NaOH中和得到主链疏水侧链亲水的接枝型两亲共聚物PBA-g-P(MAA^－Na^＋). 用Wilhelmy吊片法研究了不同浓度的两亲共聚物水溶液的表面张力, 发现其行为与小分子表面活性剂不同. 同时用动态光散射法测量了两亲共聚物水溶液中聚集体的粒度, 发现在研究的浓度范围内(0.02～10 g/L)聚集体都存在两个粒度分布峰(约30和300 nm). 浓溶液(w＝37.5%)的偏光显微照片呈现层状液晶的特征图案, 而流变研究表明此时体系具有明显的粘弹性, 说明体系形成了层状液晶. 并且用小角度X射线衍射测定了层状液晶的层间距, 约为12.6 nm.     

Effect of graft copolymer on demixing of immiscible polymers in solution

The effect of graft copolymer on the demixing of solutions of two immiscible homopolymers and critical conditions for emulsion formation were studied. The graft copolymer used in the present work consists of one backbone poly(vinyl acetate) (PVAc) and one branch polystyrene (PS). PVAc and PS of various degrees of polymerization were used as immiscible homopolymers. The common solvent was benzene. When the concentration of homopolymer blend was not sufficiently higher than the critical concentration for demixing of the blend solution, no stable emulsion was formed, even when a considerable amount of graft copolymer was present, and the added graft copolymer merely reduced the demixing rate. However, as the blend concentration was increased, a stable emulsion could readily be obtained by addition of rather small amounts of graft copolymer. The radius of emulsion droplets was inversely proportional to the weight ratio of the graft copolymer to the dispersed component polymer, in accordance with the theoretical prediction. It was concluded that the emulsions were stabilized against coagulation by graft copolymer molecules fixed strongly as a monolayer on the interface of the emulsion.     

Formation of an in situ nanosilica nanomatrix via graft copolymerization of vinyltriethoxysilane onto natural rubber

Natural rubber (NR) with an in situ nanosilica nanomatrix was characterized in present work. The in situ nanosilica nanomatrix was prepared via graft copolymerization of a silane monomer, vinyltriethoxysilane (VTES), onto deproteinized NR (DPNR) in latex stage using tetrapentamine (TEPA)/tert‐butylhydroperoxide (TBHPO) as initiators. VTES conversion of more than 80% was obtained, and it depended on VTES concentration. The graft copolymer structure was characterized by Fourier transform infrared (FT‐IR), solution‐state proton nuclear magnetic resonance (¹H‐NMR), and solid‐state ²⁹Si‐NMR spectroscopy. FT‐IR analysis of the graft copolymer confirmed the formation of in situ silica particles, while solution‐state ¹H‐NMR and solid‐state ²⁹Si‐NMR revealed the partial hydrolysis of the ethoxy groups and polycondensation of the silanol groups. The formation of nanosilica particles enhanced thermal and mechanical properties of the graft copolymer. Morphology observations of the in situ nanosilica nanomatrix through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the spherical nanosilica particles form a nanomatrix surrounding NR particle. The formation of the nanomatrix was proved to enhance mechanical properties for NR materials.     

Novel amphiphilic graft copolymers bearing hydrophilic poly(acrylic acid) backbones and hydrophobic poly(butyl methacrylate) side chains

A novel amphiphilic graft copolymer consisting of hydrophilic poly(acrylic acid) backbones and hydrophobic poly(butyl methacrylate) side chains was synthesized by successive atom transfer radical polymerization followed by hydrolysis of poly‐(methoxymethyl acrylate) backbone. A grafting‐from strategy was employed for the synthesis of graft copolymers with narrow molecular weight distributions (polydispersity index < 1.40). Hydrophobic side chains were connected to the backbone through stable C? C bonds instead of ester connections. Poly(methoxymethyl acrylate) backbone was easily hydrolyzed to poly(acrylic acid) backbone with HCl without affecting the hydrophobic side chains. The amphiphilic graft copolymer could form stable micelles in water. The critical micelle concentration in water was determined by a fluorescence probe technique. The morphology of the micelles was preliminarily explored with transmission electron microscopy and was found to be spheres. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6857–6868, 2006