温度敏感性P(MEO2MA-co-OEGMA)共聚物的合成与性质

利用原子转移自由基聚合(ATRP)方法合成了组成递变的2-甲基-2-丙烯酸-2-(2-甲氧基乙氧基)乙酯(MEO₂MA)与寡聚乙二醇甲醚甲基丙烯酸酯(OEGMA)共聚物P(MEO₂MA-co-OEGMA). 核磁共振氢谱(¹HNMR)和凝胶渗透色谱(GPC)表征了聚合物的结构、分子量及其分布. 通过测定透光率、粘度、激光粒度分析了共聚物组成对共聚物低临界溶解温度(LCST)的影响, 考察了共聚物组成、浓度、盐浓度、盐种类、温度对其溶液相行为的影响. 结果表明: 所合成的共聚物具有温度敏感性, 其LCST 可以通过合成时共聚单体MEO₂MA与OEGMA投料比的改变来调控, 随着OEGMA量的增加共聚物的LCST升高, 共聚物溶液浓度升高其LCST减小, 随盐溶液浓度的增大共聚物的LCST降低, 共聚物的LCST降低主要受盐溶液中阴离子价数的影响; HCl的引入使共聚物水溶液的LCST降低; NaOH的引入使共聚物水溶液的LCST升高.     

聚(N,N-二乙基丙烯酰胺)的合成及盐对其水溶液温敏性的影响

采用CuBr/2,2'-联二吡啶催化体系, α-溴代丙酸乙酯为引发剂, 甲醇为溶剂, 通过原子转移自由基聚合(ATRP)合成了分子量分布窄的聚(N,N-二乙基丙烯酰胺)(PDEAM). 用FT-IR、1H-NMR和凝胶渗透色谱(GPC)对其结构进行了表征; 利用透光率的测定研究了PDEAM水溶液浓度、盐以及表面活性剂对PDEAM水溶液低临界溶解温度(LCST)的影响. 结果表明: 随着PDEAM水溶液浓度的增大, LCST逐渐降低; NaCl、CH3COONa、KCl、Na2SO4及MgSO4使PDEAM水溶液的LCST降低, 降低程度与盐的种类和阴离子价数有关; 十二烷基磺酸钠(SDS)则使PDEAM水溶液的LCST升高.     

含疏水链节的聚N-异丙基丙烯酰胺共聚物的温敏性

采用溶液聚合法合成了一系列N-异丙基丙烯酰胺(NIPAM)与甲基丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯或甲基丙烯酸丁酯的无规共聚物,用浊度观测法和光散射法测定了不同共聚物水溶液的温敏相转变行为.结果表明:所得共聚物的低临界溶解温度(LCST)均低于均聚物PNIPAM的,酯类单体的结构和含量对共聚物的LCST有显著影响,其中酯基上的烷基对共聚物LCST的影响能力大于丙烯酸酯α位上的烷基,前者对增大共聚物的疏水性有更大贡献.通过NIPAM与特定丙烯酸酯单体进行无规共聚可以合成转变温度低于PNIPAM均聚物且具有预设LCST数值的水溶性温敏聚合物.     

正离子PVA基温敏性聚合物的合成与表征及其温敏性研究

通过对聚乙烯醇(PVA)进行正离子化和缩醛化改性,制备了一种新型PVA基温敏性聚合物(CAPVA),其盐水溶液表现出最低临界溶解温度(LCST).在LCST温度以下,CAPVA能溶解于水中,其水溶液清澈透明;温度高于LCST后,CAPVA聚集并从水中分离析出.利用元素、表面电荷分析和核磁共振谱对CAPVA的结构进行了表征,并用浊度法研究了正离子接枝率、缩醛度和溶液中NaCl浓度对CAPVA温敏性的影响.     

新型钴酞菁接枝温敏聚合物的制备及性能

采用2,4,6-三氯-1,3,5-三嗪对四氨基钴酞菁进行改性,并以共价键接枝到聚N-异丙基丙烯酰胺上制得一种新型温敏性高分子催化剂——钴酞菁接枝温敏聚合物,并采用UV-Vis、TG等对其进行表征.对钴酞菁接枝温敏聚合物、温敏聚合物和小分子金属酞菁进行溶解性测试,结果表明与四氨基钴酞菁相比,所合成的钴酞菁接枝温敏聚合物能溶解于水和大多数有机溶剂,且该聚合物水溶液具有良好的温敏性,其最低临界溶解温度(LCST)为34.5℃.采用浊度法考察了不同比例的混合溶剂(乙醇/水、DMF/水)对LCST的影响,结果表明随着有机溶剂含量的增加,LCST先下降后升高,而当有机溶剂增加到一定程度时温敏性消失.本文还考察了钴酞菁接枝温敏聚合物对2-巯基乙醇的催化活性,结果表明随着温度升高,催化活性也不断提高,而当温度超过LCST时催化活性急剧下降,聚合物从溶液中析出.基于这些特性,该温敏聚合物负载酞菁作为一种新型的催化剂可实现均相催化、异相分离.     

丙烯酸β-羟丙酯/乙烯基吡咯烷酮水凝胶的合成和热敏行为的研究

用自由基共聚法合成了一系列 β -羟丙酯 ( β -HPAT)和乙烯基吡咯烷酮 (NVP)的共聚物及其水凝胶。发现共聚物的水溶液有敏锐的温敏行为 ,最低汇溶温度 (LCST)随NVP含量的增加而升高 ,随着反应单体总浓度的增加 ,相变敏锐性下降且LCST也随之下降。通过考察水凝胶的溶胀率 (SR) ,发现共聚凝胶在适当的单体浓度 ,交联剂浓度和较宽的单体浓度配比范围内 ,有较灵敏的温敏行为。     

温敏性共聚物P(DMA-co-DAAM)的合成与热缔合行为研究

以N,N-二甲基丙烯酰胺(DMA)和双丙酮丙烯酰胺(DAAM)为共聚单体,在水溶液中采用常规自由基聚合以K_2S_2O_8-Na_2SO_3双氧化还原体系为引发剂,合成了一系列具有最低临界溶解温度(LCST)的温敏性聚合物P(DMA-co-DAAM).采用紫外可见分光光度计、动态光散射、芘荧光探针法和变温核磁共振氢谱等多种手段研究共聚物在不同温度下的溶液结构,结果表明共聚物P(DMA-co-DAAM)具有明显的热致缔合行为,在低温下聚合物以单链形式溶解,温度升高超过LCST之后由于P(DMA-co-DAAM)分子链上DAAM侧基发生亲水-疏水性变化,部分疏水链段缔合形成微相分离的胶束聚集体.进一步的研究还表明通过改变共聚物组成和溶液浓度能够有效调节共聚物溶液的缔合转变温度,共聚物P(DMA-co-DAAM)的LCST值与DAAM含量成很好的线性关系,DAAM含量越高LCST温度越低.采用常规自由基聚合所带来的链间异质性以及分子量的多分散性等特点并没有显著影响共聚物P(DMA-co-DAAM)的温敏性.     

温度/pH敏感性嵌段共聚物P(HEMA-co-DEAEMA)-b-PDEAM-b-P(DEAEMA-co-HEMA)的合成与性质研究

利用原子转移自由基聚合方法(ATRP)合成了组成递变的嵌段共聚物P(HEMA-co-DEAEMA)-b-PDEAM-b- P(DEAEMA-co-HEMA). 用FTIR, ¹H NMR和GPC技术表征了聚合物的组成、结构、分子量及其分布. 通过透光率测定、粘度、激光粒度分析和透射电镜研究了共聚物组成、温度及溶液pH对其溶液相行为和胶束化作用的影响. 结果表明: 所合成的嵌段共聚物具有温度和pH敏感性, 共聚物水溶液的低临界溶解温度(LCST)随HEMA量的增加而降低, 临界相变pH随HEMA量的增加而降低, 温度和pH诱导均可实现嵌段共聚物的胶束化. 控制HEMA量可以调控嵌段共聚物的LCST和pK_a.     

葡萄糖基N-异丙基丙烯酰胺共聚物合成及其温敏性

采用酶促法合成了可聚合的葡萄糖乙烯酯衍生物6-O-乙烯己二酰-D-葡萄糖(OVAG),通过自由基聚合法将N-异丙基丙烯酰胺和OVAG共聚,制备出了温敏含糖共聚物poly(OVAG-co-NIPAAm),通过1H NMR对聚合物的结构进行了表征,用凝胶色谱测定共聚物的相对分子质量。用可见光吸收法测定了poly(OVAG-co-NIPAAm)的低临界溶解温度(LCST),动态光散射测定了聚合物在水溶液中的流体力学直径,静态光散射测定了共聚物在水溶液中的均方旋转半径。结果表明,采用自由基聚合制备的温敏含糖共聚物在水溶液中自组装成近似球形的纳米粒子,其LCST由N-异丙基丙烯酰胺均聚物的32℃提高至39℃,粒径在60 nm左右,粒径分布较窄。     

N-异丙基丙烯酰胺/丙烯酸胆甾醇酯共聚物研究

合成和表征了N 异丙基丙烯酰胺 (NIPAM)与丙烯酸胆甾醇酯 (CHA)的共聚物 .利用表面张力和荧光探针法研究了共聚物水溶液的表面活性性能 ,确定了其临界胶束浓度 (CMC) .利用浊度法和荧光探针法测定了共聚物的最低临界溶液温度 (LCST) .研究发现 ,在聚N 异丙基丙烯酰胺 (PNIPAM)分子链中引入疏水结构单元CHA会使其LCST下降 ;且随着共聚物中CHA含量的增加 ,LCST下降幅度增加 .在PNIPAM链段中引入少量的CHA就会使其表现出明显的两亲性 ,共聚物在水中能形成有壳核结构的稳定胶束 .通过将疏水化合物胆甾醇作为模拟药物包埋在胶束的疏水核中的研究 ,证实所得的胶束能包埋疏水药物 ,且随着包埋胆甾醇含量的增加 ,胶束平均粒径增大 .     

温敏性含氟两亲接枝共聚物的制备及胶束化行为

以聚乙二醇单甲醚甲基丙烯酸酯(MPEGMA)为大分子单体, 甲基丙烯酸六氟丁酯(HFMA)为含氟单体, N-异丙基丙烯酰胺(NIPAAm)为功能性单体, 采用大分子单体接枝共聚法, 制备了一种温敏性含氟两亲接枝共聚物P(NIPAAm-co-HFMA)-g-PEG. 利用FTIR, ¹H NMR, ¹⁹F NMR和GPC对共聚物的结构进行表征; 采用紫外-可见分光光度计测定了共聚物的低临界溶解温度(LCST)约为38.9 ℃, 高于人体正常的生理温度; 利用荧光探针技术测定了共聚物的临界胶束浓度(cmc), 结果表明, 当共聚物溶液温度高于LCST时, 其cmc明显变小; 利用激光光散射粒度仪(LLS)测定了共聚物胶束的水合粒径及其分布, 当温度达到LCST时, 胶束粒径明显变小, 温度过高时, 粒径又有所增大; 利用透射电子显微镜(TEM)研究了共聚物胶束的形貌, 结果表明, P(NIPAAm-co-HFMA)-g-PEG在水溶液中可自组装成球状胶束粒子, 随着温度的升高, 共聚物胶束由松散的核壳结构转变成更加紧凑的球状结构, 且粒径明显变小.     

全亲水无规共聚物P(NIPAM-co-AA)的pH和温度双重刺激响应性水相自组装

从N-异丙基丙烯酰胺（NIPAM）和丙烯酸（AA）单体合成了一种全亲水无规共聚物P（NIPAM-co-AA）,实验发现该聚合物在水相中可以产生pH或温度双重刺激响应性自组装. 采用透射电子显微镜（TEM）观察了自组装体的形貌,采用动态光散射（DLS）和静态光散射（SLS）观察了其粒径及粒径分布. 测定了该聚合物水溶液的最低临界溶解温度（LCST）及其zeta 电位随pH的变化,通过分析NIPAM和AA两种链节的质子化状态随温度和pH变化的趋势,阐释了其在水相中产生双重响应性自组装的推动力;并结合傅里叶红外（FT-IR）光谱测定自组装体表面富集基团的结果,进一步阐释了不同环境下自组装体的微结构. 这类全亲水无规共聚物的合成方法简单,具有pH和温度双重响应性,其全水相中的刺激响应性自组装行为在药物释放等方面具有潜在的应用价值.     

Solubility behavior of amphiphilic block and random copolymers based on 2‐ethyl‐2‐oxazoline and 2‐nonyl‐2‐oxazoline in binary water–ethanol mixtures

The solution properties of random and block copolymers based on 2‐ethyl‐2‐oxazoline (EtOx) and 2‐nonyl‐2‐oxazoline (NonOx) were investigated in binary solvent mixtures ranging from pure water to pure ethanol. The solubility phase diagrams for the random and block copolymers revealed solubility (after heating), insolubility, dispersions, micellization as well as lower critical solution temperature (LCST) and upper critical solution temperature behavior. The random and block copolymers containing over 60 mol % pNonOx were found to be solubilized in ethanol upon heating, whereas the dissolution temperature of the block copolymers was found to be much higher than for the random copolymers due to the higher extent of crystallinity. Furthermore, the block copolymer containing 10 mol % pNonOx exhibited a LCST in aqueous solution at 68.7 °C, whereas the LCST for the random copolymer was found to be only 20.8 °C based on the formation of hydrophobic microdomains in the block copolymer. The random copolymer displayed a small increase in LCST up to a solvent mixture of 9 wt % EtOH, whereas further increase of ethanol led to a decrease in LCST, which is probably due to the “water‐breaking” effect causing an increased attraction between ethanol and the hydrophobic part of the copolymer. In addition, the EtOx‐NonOx block copolymers revealed the formation of micelles and dynamic light scattering demonstrated that the micellar size is increasing with increasing the ethanol content due to the enhanced solubility of EtOx. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 515–522, 2009     

Thermosensitive copolymers having soluble and insoluble monomer units,poly(N‐vinylacetamide‐co‐methyl acrylate)s: Effect of additives on their lower critical solution temperatures

New thermosensitive polymers were synthesized by copolymerization between N‐vinylacetamide (NVA) and methyl acrylate whose homopolymers are soluble and insoluble in water, respectively. The lower critical solution temperature (LCST) of the obtained copolymers ranged between 59 and 83 °C, and the LCST increased with an increasing NVA content in the copolymers. The effectiveness of various salts addition on lowering the LCST of the copolymer solutions followed Hoffmeister series. NaCl and Na₂SO₄ addition linearly lowered the LCST with an increasing salts concentration, and slopes of the lines were almost constant regardless of the copolymer composition. The effectiveness of alcohols with various alkyl chain lengths on lowering the LCST did not follow the viscosity B coefficient values of the alcohols, which was probably the result of preferential adsorption of the alcohols to the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2651–2658, 2004     

Phase transition of aqueous solutions of poly(N,N-diethylacrylamide-co-acrylic acid) by differential scanning calorimetric and spectrophotometric methods

 The phase transition of aqueous solutions of poly(N,N-diethylacrylamide-co-acrylic acid) (DEAAm–AA) is studied by differential scanning calorimetry (DSC) and UV–vis spectrophotometry. The copolymer aqueous solutions are shown to have well-defined lower critical solution temperatures (LCSTs). The LCST values obtained from the maximum of the first derivatives of the DSC and optical transition curves agree well. DSC can be used to measure the phase-transition temperature of more dilute polymer solutions. On increasing the AA composition in the copolymers, the LCST values of the copolymer increase, then decrease at higher AA composition. For the aqueous solution of the copolymers, the transition curve obtained by the spectrophotometric method is highly wavelength dependent. The LCST values are found to be concentration-dependent. The changes in the heat of the phase transition of the copolymer solutions measured from DSC are lower than that of the homopolymer PDEAAm solution. This is consistent with the suggestion that the polymer chains of the copolymers collapsed only partially at temperatures above the LCST. The added salt (sodium chloride) decreases the transition temperature of the polymer solution. Received: 14 November 2000 Accepted: 15 January 2001     

Influence of multiple stimuli on the lower critical solution temperature of new cationic poly(N‐acryloyl‐N′‐ethylpiperazine‐co‐N‐isopropylacrylamide) solutions

New multi‐stimuli responsive cationic copolymers based on N‐acryloyl‐N′‐ethyl piperazine (AcrNEP) and N‐isopropylacrylamide (NIPAM) were prepared by thermal free‐radical solution polymerization in dioxane at 75 °C. The chemical composition of the copolymers was determined by ¹H NMR spectroscopy and was found that the copolymers were slightly rich in NIPAM content than that of AcrNEP. The reactivity of the two monomers for the copolymerization reaction was evaluated by the extended Kelen‐Tüdös method. The distribution of monomer sequence in the copolymer chain was estimated using the terminal copolymerization model. The maximum tendency to alternation (～ 70%) was at 60 mol % of AcrNEP in the monomer feed. The copolymers were readily soluble in water at room temperature at all compositions and exhibited well‐defined lower critical solution temperature (LCST) phenomenon. The influence of various stimuli such as pH, temperature, simple inorganic salts, and surfactants on the LCST of the copolymers was studied in detail. Simple inorganic salts such as sodium chloride, sodium bromide, and sodium sulfate showed a salting‐out effect while sodium iodide showed a salting‐in effect. The salting‐out coefficient of the salts were calculated using the Sestchenow method, and the salting trend followed the order SO₄^2? > Cl^? > Br^? > I^?. The divalent salt was more effective in lowering the LCST than the monovalent salts. The cationic surfactant hexadecyl trimethylammonium bromide at concentrations above the critical micelle concentration caused a gradual increase in the LCST of the copolymer solutions. The intrinsic viscosity and light scattering behavior of the copolymers in water and in sodium chloride solutions were studied in detail. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1175–1183     

全亲水无规共聚物P(NIPAM-co-AA)的pH和温度双重刺激响应性水相自组装

从N-异丙基丙烯酰胺(NIPAM)和丙烯酸(AA)单体合成了一种全亲水无规共聚物P(NIPAM-co-AA),实验发现该聚合物在水相中可以产生pH或温度双重刺激响应性自组装.采用透射电子显微镜(TEM)观察了自组装体的形貌,采用动态光散射(DLS)和静态光散射(SLS)观察了其粒径及粒径分布.测定了该聚合物水溶液的最低临界溶解温度(LCST)及其zeta电位随pH的变化,通过分析NIPAM和AA两种链节的质子化状态随温度和pH变化的趋势,阐释了其在水相中产生双重响应性自组装的推动力;并结合傅里叶红外(FT-IR)光谱测定自组装体表面富集基团的结果,进一步阐释了不同环境下自组装体的微结构.这类全亲水无规共聚物的合成方法简单,具有pH和温度双重响应性,其全水相中的刺激响应性自组装行为在药物释放等方面具有潜在的应用价值.     

Thermo‐ and pH‐responsive gradient and block copolymers based on 2‐(2‐methoxyethoxy)ethyl methacrylate synthesized via atom transfer radical polymerization and the formation of thermoresponsive surfaces

A series of gradient and block copolymers, based on 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO₂MA) and tert‐butyl acrylate (^tBA), were synthesized by atom transfer radical polymerization (ATRP) in a first step. The MEO₂MA monomer leads to the production of thermosensitive polymers, exhibiting lower critical solution temperature (LCST) at around room temperature, which could be adjusted by changing the proportion of ^tBA in the copolymer. In a second step, the tert‐butyl groups of ^tBA were hydrolyzed with trifluoroacetic acid to form the corresponding block and gradient copolymers of MEO₂MA and acrylic acid (AA), which exhibited both temperature and pH‐responsive behavior. These copolymers showed LCST values strongly dependent on the pH. At acid pH, a slightly decrease of LCST with an increase of AA in the copolymer was observed. However, at neutral or basic conditions, ionization of acid groups increases the hydrophilic balance considerably raising the LCST values, which even become not observable over the temperature range under study. In the last step, these carboxylic functionalized copolymers were covalently bound to biocompatible and biodegradable films of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(HB‐co‐HHx)] obtained by casting and, previously treated with ethylenediamine (ED) to render their surfaces with amino groups. Thereby, thermosensitive surfaces of modified P(HB‐co‐HHx) could be obtained. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

N-异丙基丙烯酰胺/丙烯酸十八酯共聚物水溶液胶束及相分离行为研究

合成了N异丙基丙烯酰胺(NIPAM)和丙烯酸十八酯(ODA)的共聚物.利用荧光探针和滴重法研究了NIPAMODA共聚物在水溶液中的胶束形成过程.同时还利用荧光探针法研究了共聚物水溶液在温度升高时出现的LCST(LowerCriticalSolutionTemperature)现象,表明该高分子在温度升高时存在着相分离现象.利用LB技术测量共聚物不溶单分子膜的PA曲线,发现随着温度升高共聚物的单分子膜越来越凝聚的反常现象,这从另一个侧面证实了共聚物NIPAMODA的相分离行为,并对此现象作了讨论.