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.     

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.     

由聚丙二醇二缩水甘油醚和甘油制备温敏性超支化聚合物

由聚丙二醇二缩水甘油醚和甘油通过质子转移聚合(proton transfer polymerization)一步法制备了端羟基的温敏性超支化聚醚.聚合产物的分子量(Mn)在1.76×104~2.43×104之间,玻璃化转变温度(Tg)在-31.5~-26.7℃之间,热分解温度(Td)在367~376℃之间.通过控制聚丙二醇二缩水甘油醚和甘油的投料比,实现了对温敏性超支化聚醚最低临界溶解温度(LCST)的调节,LCST可控制在28.3~39.6℃之间.     

基于超支化温敏聚合物制备温敏金纳米粒子

通过对不同分子量的超支化聚乙烯亚胺(hyperbranched polyethyleni mine,HPEI)的端基进行部分或完全异丁酰胺(isobutyric amide,IBAm)化,可以制备一系列具有不同低临界溶解温度(Lower Critical SolutionTemperature,LCST)的超支化温敏聚合物HPEI-IBAm。通过离子键或氢键之间的相互作用,所得超支化温敏聚合物可以吸附于柠檬酸钠还原并稳定的14nm的金纳米粒子(AuNP)的表面,从而得到具有温敏性质的金纳米粒子。所得温敏金的LCST都低于其相应的温敏聚合物,其差值在0.8至6℃之间。在pH值为9.18的缓冲溶液中,通过改变所用聚合物的分子量以及异丁酰胺基团的取代度,所得温敏金的LCST可控制在21.7~48.2℃之间。此外,所得温敏金的LCST也是pH值敏感的,通过溶液pH值的改变,所得温敏金的LCST值可以在更宽的范围内调节。增加溶液的碱性,LCST可能变化不大或降低,减小溶液的碱性会使LCST升高,直到消失。在偏酸的条件下,所得金复合物通常发生聚集,变得不稳定。此外,溶液中的盐度对所得温敏金的LCST也有影响,氯化钠和硫酸钠会降低其LCST,尤其是硫酸钠的效果更显著。     

表面张力法研究温敏性接枝共聚物的微胶束化行为

用表面张力法研究了以水溶性可生物降解的葡聚糖为主链 ,具有温敏相变特性的聚 (N 异丙基丙烯酰胺 )为接枝链的葡聚糖 接枝 聚 (N 异丙基丙烯酰胺 ) (Dextran g PNIPAM)共聚物在水溶液中的胶束化行为 .研究结果表明Dextran g PNIPAM体系的微胶束化行为与共聚物结构和溶液体系的温度密切相关 ,接枝共聚物中PNIPAM含量越大 ,水溶液体系的温度越高 ,形成胶束的临界胶束浓度 (CMC)越小 .特别值得指出的是 ,无论水溶液的温度是否高于PNIPAM接枝链段的相变温度 (LCST) ,即PNIPAM链段由亲水性转变为疏水性的温度 ,Dextran g PNIPAM均呈现一个临界胶束浓度大 ,对该现象给予了解释 .     

具有可控温敏相变行为的四氢呋喃-缩水甘油超支化共聚醚的合成

采用四氢呋喃(THF)和缩水甘油(glycidol)进行阳离子开环共聚,一步合成了主链中含有柔性聚四氢呋喃线型链段的温敏性超支化共聚醚.采用定量13C-NMR确定了共聚醚的超支化结构,同时计算了其支化度.利用体积排除色谱-多角度激光光散射(SEC-MALLS)对聚合物分子量及分布进行了表征.紫外-可见光光谱(UV)测试发现共聚醚水溶液透过率在最低临界溶解温度(LCST)附近呈现剧烈变化,但是其相变速率缓慢,相变平衡时间可达30 min;且聚合物溶液的相变速率和紫外光透过率变化具有温度依赖性.采用透射电镜(TEM)对相变过程观察后发现,这种缓慢相变过程是由于超支化共聚醚组装形成的胶束随温度升高发生不同程度聚集所致.     

聚(甲基丙烯酸N,N-二甲氨基乙酯)的温度和pH敏感性及其对乳液稳定性的影响

甲基丙烯酸N,N-二甲氨基乙酯的均聚物(PDMAEMA)在水中的溶解性具有温敏性,即低温溶解、高温不溶,而且其低临界溶液温度(LCST)与pH密切相关.本文重点考察了PDMAEMA水溶液在不同温度、pH值、溶液离子强度时的相转变特性,并研究了水溶液中乳化剂对PDMAEMA的疏水相互作用和增溶稳定作用.将PDMAEMA的温敏相转变行为同有关乳液的稳定性相关联,揭示了改善乳液稳定性的内在机制.     

P(MMA-co-MAh)-g-mPEG的合成及环境敏感性

采用偶合接枝法在甲基丙烯酸甲酯(MMA)和马来酸酐(MAh)无规共聚物上接枝不同含量的聚乙二醇单甲醚(mPEG), 合成具有pH敏感和温度敏感的两亲接枝共聚物P(MMA-co-MAh)-g-mPEG, 并对其进行了红外光谱和核磁共振波谱表征. 通过紫外-可见分光光度计测量了接枝共聚物水溶液的透光率, 结果表明, 接枝聚合物的水溶液呈现低临界溶解温度(LCST), 其LCST值对环境pH值和无机盐等因素敏感, 并可通过控制亲水侧链含量来调节.     

易衍生化温敏高分子刷的制备及其温敏行为研究

温敏材料由于优异的性能和潜在的应用价值而具有良好的发展前景.利用超分子自组装单层(SAM)与表面引发聚合(SIP)技术将2-(2-甲氧乙氧基)甲基丙烯酸乙酯(MEO2MA)与聚乙二醇甲基丙烯酸酯(OEGMA526)的共聚物poly(MEO2MAco-OEGMA526)接枝于金表面,探索了不同引发剂溶液浓度(χIsol)、单体OEGMA526摩尔浓度(C526)与干态膜厚度(d)对该高分子刷性质的影响.应用石英晶体微天平(QCM)对其温敏行为进行研究,结果表明:在χIsol=1%与C526=5%条件下制备的高分子刷,最低临界溶解温度(LCST)为34℃;其LCST由OEGMA526的单体摩尔浓度决定,不受膜厚的影响.该高分子刷在接枝生物素后其与链霉亲和素的结合实验证明,高分子刷末端的羟基为其官能团化提供了契机.该易衍生化温敏高分子刷为发展新型温敏材料提供了研究基础.     

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.     

Properties of a novel thermal sensitive polymer based on poly(vinyl alcohol) and its layer‐by‐layer assembly

Structurally modified poly(vinyl alcohol) (PVA) was prepared as novel thermally sensitive polymers by partially acetalyzing and/or ionizing the commercially available PVA. Their aqueous solutions experience completely reversible polymer aggregation and dissolution above and below the lower critical solution temperature (LCST), respectively. The LCST of a partially acetalyzed PVA (APVA) can be readily controlled by the degree of acetalysis or the molecular weight of the starting PVA. Introduction of a small amount of cationic group onto the APVA backbone increases the LCST obviously, while the LCST is highly sensitive to NaCl concentration. Then APVA and cationic APVA multilayers are assembled on rayon to make a thermal responsive fiber. The atomic force microscopy (AFM) images of the surface reveal the increment of roughness stimulated by temperature. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and characterization of cationic poly vinyl alcohol with a low degree of substitution

The cationization of polymers has been regarded as an effective method to improve their performance for various applications. In this work, the cationization of poly vinyl alcohol (PVA) was investigated under different conditions, i.e., various glycidyl-trimethylammonium chloride (GTMAC) to PVA ratios, reaction temperatures, times, PVA and NaOH concentrations and solvent compositions. The results showed that the overall efficiency of the cationic modification was rather low, which was due to the hydrolysis of both GTMAC and cationic-modified PVA (CPVA) under the strong alkaline conditions employed. The results also showed that the optimum GTMAC/PVA ratio depended on the solvent composition. The cationization was confirmed by means of ¹H NMR and FTIR analyses. The maximum efficiency in water was obtained under the conditions of 95 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration, while that in the ethanol/DMSO mixture (1.25 v/v) was obtained under the conditions of 70 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration. Additionally, the interaction of CPVAs with a silicon wafer (as a substrate) was determined by employing an atomic force microscope (AFM) in water and air.     

一种温度/pH敏感性聚合物的合成及其溶液性能研究

通过官能团的合理设计,将具有亲水性的阳离子与具有疏水作用的苄基结合在同一单体上,合成出了具有潜在温度和pH敏感性的新型单体——二甲基苄基(2-甲基丙烯酰氧乙基)溴化铵(DMBMAAB),并用1H-NMR和液相色谱法对其结构和纯度进行了表征.DMBMAAB与丙烯酰胺(AM)在水溶液中通过自由基聚合合成出共聚物P(DMBMAAB-co-AM),用核磁和元素分析法对其结构和组成进行了表征.P(DMBMAAB-co-AM)的水溶液表现出了与聚异丙基丙烯酰胺(PNIPAAm)相反的温度响应特性,PNIPAAm具有最低临界溶解温度(LCST),而P(DMBMAAB-co-AM)具有最高临界溶解温度(HCST).当温度从50℃上升到70℃的过程中,P(DMBMAAB-co-AM)共聚物溶液的透光率和表观粘度(表观性能)发生了急剧的变化,溶液外观由乳状液变为澄清液;另一个与PNIPAAm显著不同的特性是,该聚合物还具有非常明显的pH敏感性.当pH值从11变到12时,溶液的表观性能也发生了相当剧烈的变化.此外,表面活性剂(SDS)、盐(NaCl)等外界因素也对P(DMBMAAB-co-AM)共聚物溶液的表观性能具有明显的影响.结果表明,P(DMBMAAB-co-AM)是一种具有多重响应的新型功能聚合物材料,分子链中亲水和疏水基团间的相互作用以及环境的变化是引起这一系列响应行为的主要原因.     

温度及pH敏感聚(丙烯酸)/聚(N-异丙基丙烯酰胺)互穿聚合物网络水凝胶的合成及性能研究

合成聚（丙烯酸）／聚（Ｎ 异丙基丙烯酰胺）互穿聚合物网络（ＰＡＡｃ／ＰＮＩＰＡＩＰＮ）水凝胶，具有温度及ｐＨ双重敏感特性．这种水凝胶在弱碱性条件下的溶胀率远大于酸性条件下的溶胀率．在酸性条件下，随着温度上升，凝胶的溶胀率也随之逐渐上升；而在弱碱性条件下，温度低于聚（Ｎ 异丙基丙烯酰胺）（ＰＮＩＰＡ）的较低临界溶解温度（ＬＣＳＴ）时，溶胀率也随着温度的上升而上升，当温度达到ＬＣＳＴ时，凝胶的溶胀率突然急剧下降，并随着温度的逐渐上升而下降．     

Recent approaches for clickable poly(2-oxazoline)-based functional stimuli-responsive polymers and related applications

Abstract

Poly(2-oxazoline)s (POxs) are well-known thermo-responsive polymers that exhibit reversible hydrophilic–hydrophobic phase transitions at the lower critical solution temperature (LCST). Using living cationic ring-opening polymerisation, various functional groups can be introduced into POxs. Several clickable POxs with propargyl or azide end groups have been designed and subsequently reacted with various functional groups to prepare multifunctional POxs that respond to stimuli such as temperature, pH, chemicals and light. In this article, we briefly review recent approaches for clickable POx-based functional stimuli-responsive polymers and related applications.     

Pervaporation separation of water-acetic acid mixtures through poly(vinyl alcohol) membranes crosslinked with glutaraldehyde

Poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by a solution method for the pervaporation separation of acetic acid-water mixtures. In the solution method, dry PVA films were crosslinked by immersion for 2 days at 40°C in reaction solutions which contained different contents of GA, acetone and a catalyst, HCl. In order to fabricate the crosslinked PVA membranes which were stable in aqueous solutions, acetone was used as reaction medium in stead of aqueous inorganic salt solutions which have been commonly used in reaction solution for PVA crosslinking reaction. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of GA was characterized by IR spectroscopy. Swelling measurements were carried out in both water and acetic acid to investigate the swelling behavior of the membranes. The swelling behaviour of a membrane fabricated at different GA content in a reaction solution was dependent on crosslinking density and chemical functional groups created as a result of the reaction between PVA and GA, such as the acetal group, ether linkage and unreacted pendent aldehydes in PVA. The pervaporation separation of acetic acid-water mixtures was performed over a range of 70–90 wt% acetic acid in the feed at temperatures varying from 35 to 50°C to examine the separation performances of the PVA membranes. Permeation behaviour through the membranes was analyzed by using pervaporation activation energies which had been calculated from the Arrhenius plots of permeation rates.     

Living cationic polymerization of vinyl ethers in the presence of added bases: Recent advances

The living cationic polymerization of vinyl ethers was carried out with organoaluminum compounds in the presence of various types of esters and ethers (cyclic and acyclic), to find out the suitable added bases available for the living polymerization. The effects of the basicity and steric hindrance of added bases were investigated in detail. On the basis of these results, a fast living polymerization system was realized. To synthesize water-soluble polymers such as thermally-induced phase separating polymers and polyalcohols with well-defined polymer structure, the living polymerization of various vinyl ethers was examined. The aqueous solution of living poly(vinyl ethers) having oxyethylene units exhibited a quite sensitive (ΔT_ps=0.3–0.5°C) and reversible phase separation on heating and cooling. The effects of polymer structures (pendant substituent, polymer sequence, molecular weight, and MWD) on the phase separation behavior were investigated. PVA and block copolymers containing PVA units with a narrow MWD were also prepared via living cationic polymerization of vinyl ethers and a deprotection reaction.     

Reversible changes in solution pH resulting from changes in thermoresponsive polymer solubility

Pendant groups on polymers that have lower-critical solution temperature (LCST) properties experience a water-like environment below the LCST where the polymer is soluble but are less hydrated above the LCST when the polymer phase separates from solution. When these pendant groups are amphoteric groups like carboxylate salts or ammonium salts, the change in solvation that accompanies the polymer precipitation event significantly changes these groups' acidity or basicity. These changes in acidity or basicity can lead to carboxylate salts forming carboxylic acid groups by capturing protons from the bulk solvent or ammonium salts reverting to the neutral amine by release of protons to the bulk solvent, respectively. When polymers like poly(N-isopropylacrylamide) that contain a sufficient loading of such comonomers are dissolved in solutions whose pH is near the pK(a) of the pendant acid or basic group and undergo an LCST event, the LCST event can change the bulk solution pH. These changes are reversible. These effects were visually followed using common indicators with soluble polymers and or by monitoring solution pH as a function of temperature. LCST events triggered by the addition of a kosmotropic salt lead to similar reversible solution pH changes.     

Surfactant effect on the lower critical solution temperature of poly(organophosphazenes) with methoxy-poly(ethylene glycol) and amino acid esters as side groups

 The surfactant effect on the lower critical solution temperature (LCST) of thermosensitive poly(organophosphazenes) with methoxy-poly(ethylene glycol) and amino acid esters as side groups was examined in terms of molecular interactions between the polyphosphazenes and surfactants including various anionic, cationic, and nonionic surfactants in aqueous solution. Most of the anionic and cationic surfactants increased the LCST of the polymers: the LCST increased more sharply with increasing length and hydrophobicity of the hydrophobic part of the surfactant molecule. The ΔLCSTs (T _0.03M− T _0M), the change in the LCST by addition of 0 and 0.03 M sodium dodecyl sulfate (SDS), were found to be 7.0 and 14.5 °C for the polymers bearing ethyl esters of glycine and aspartic acid, respectively. The LCST increase of poly(organophosphazene) having a more hydrophobic aspartic acid ethyl ester was 2 times larger compared with that of the polymer having glycine ethyl ester as a side group. The binding behavior of SDS to the polymer bearing glycine ethyl ester as a hydrophobic group was explained from the results of titration of the polymer solutions containing SDS with tetrapropylammonium bromide. Graphic models for the molecular interactions of polymer/surfactant and polymer/surfactant/salt in aqueous solutions were proposed. Received: 17 February 2000/Accepted: 25 April 2000     

A rheological study of cationic micro- and nanofibrillated cellulose: quaternization reaction optimization and fibril characteristic effects

Driven by the demand for various cationic biopolymers in recent years, the quaternization of cellulose nanofibers was carefully investigated to have tight control over their final characteristics. The addition of sodium hydroxide (NaOH) to the reaction mixture is crucial as it catalyzes the conversion of alcohol groups of cellulose into more reactive alcoholate groups. On the other hand, excessive concentration proves to inhibit the reactivity of hydroxyl groups. The addition of glycidyltrimethylammonium chloride (GTMAC) increases the yield of the trimethylammonium chloride content (TMAC) reaction, while in excess it affects the rheological properties of the quaternizated cellulose nanofibers. The effects of NaOH and GTMAC on the TMAC content and rheological properties have been investigated in detail and mathematically evaluated. Furthermore, a comparison of the viscoelastic behavior and shear thinning character of commercial cationic micro- and nanofibrillated cellulose is presented. The research allows to extend the possibility of using cellulose in many applications of cationic biopolymers.