温度/光双重响应性树枝状单体的合成与表征

通过重氮、还原、取代、醚化、酯化等反应,合成了具有温敏和光敏基团的新型双功能性树枝状单体,采用红外光谱(FTIR)、核磁共振(~1HNMR、~(13)CNMR)、质谱(MS)对目标产物进行了表征;通过紫外可见分光光度计(UVVis)对单体水溶液的温敏性和光敏性进行了研究。结果表明:单体水溶液(1 mg/m L)的低临界溶解温度(LCST)为12.5℃;紫外光照射后,LCST降低了6.3℃,同时,单体水溶液对紫外可见光的吸收具有良好的可逆性。     

N-异丙基丙烯酰胺/N-羟甲基丙烯酰胺共聚物及其水凝胶的合成与温敏性研究

通过自由基聚合合成了N-异丙基丙烯酰胺(NIPAm)与-羟甲基丙烯酰胺(NHMPA)的共聚物及其水凝胶。研究发现,调节两单体的配比可得到不同的低临界溶液温度(LCST)值的共聚物及水凝胶。结果表明,NHMPA的加入不改变PNIPAm的温敏性,但可有效地调节其LCST值。     

原位一步法制备温敏改性纳米二氧化硅

采用原位一步法合成了温敏改性聚 N-异丙基丙烯酰胺(PNIPAAm)/SiO2纳米复合物. 通过接触角对温敏改性的纳米SiO2进行了条件优化：反应温度73℃,反应时间6 h,单体用量与KH-570摩尔比为1:1,引发剂用量为单体用量与KH-570总质量的2.5%。通过TEM、FT-IR、XPS等手段对温敏性纳米SiO2的组成和结构进行了表征。同时,这一有机-无机纳米复合物仍然保持PNIPAAm 的温度响应性, 最低临界溶解温度(LCST)与纯PNIPAAm相似。     

温敏性PEG水凝胶的合成及性能

以聚乙二醇二丙烯酸酯(PEGDA)和3,6-二氧杂-1,8-辛二硫醇(EDT)为原料,利用巯基-迈克尔加成法,合成了温敏性聚合物poly(PEGDA-alt-EDT)。通过1HNMR、GPC、UV-vis和DLS表征了共聚物的结构、相对分子质量、低临界溶解温度(LCST)及其在水中的聚集状态。以PEGDA_(600)(Mn=600)为原料合成的poly(PEGDA_(600)-alt-EDT)在过硫酸铵的引发/催化下末端官能团进一步发生偶合-聚合反应,形成了温敏性的水凝胶。测试了水凝胶的温敏、吸水溶胀和流变性能;利用SEM观察了凝胶的微观结构和形貌。结果表明:当w[poly(PEGDA_(600)-alt-EDT)]=0.1%和1.0%时,其水溶液的LCST分别为69和49℃;PEGDA的数均相对分子质量(Mn)由600增加到1 000时,相应共聚物的LCST可由49℃调节到66℃;poly(PEGDA_(600)-alt-EDT)水凝胶的相转变温度约34℃;水凝胶poly(PEGDA_(600)-alt-EDT)中水的质量分数为77%时,凝胶的储能模量高达2.9×104Pa,相应的损耗因子低至0.04;在15~60℃内,随温度升高,凝胶的平衡溶胀比(SR)由324%降至69%;干燥的凝胶呈柔韧的橡胶态。     

温敏性双亲水含半乳糖共聚物的合成及其胶束的自组装

采用酶促法合成与可逆加成-链断裂转移自由基聚合(RAFT聚合)有效结合的方法,制备相对分子质量(简称分子量,下同)分散系数(PDI)较低的温敏性含糖共聚物Poly(DEGMA-co-OVNG)。通过核磁共振氢谱(1HNMR),傅里叶变换红外光谱(FTIR),凝胶渗透色谱(GPC)对聚合物结构进行了表征。通过紫外-可见光谱(UV-vis)研究表明,共聚物的低临界溶解温度(LCST)可以通过共聚单体的比例进行调控,当DEGMA与OVNG的物质的量之比为8∶1时,含糖共聚物的LCST值为36℃。在37℃生理温度下,Poly(DEGMA-co-OVNG)可以自组装形成纳米胶束,透射电子显微镜(TEM)显示自组装形成的聚合物胶束是结构均匀、形貌规整的球形,通过动态光散射(DLS)测得纳米微球的粒径约为121 nm,该温敏性含糖共聚物在药物载体方面具有潜在的应用前景。     

pH、温度和光三重敏感的PDMAEMA-AZO的研究

在含偶氮苯的三硫酯链转移剂（CTA-AZO）存在下，将甲基丙烯酸二甲氨基乙酯（DMAEMA）通过可逆加成断裂链转移（RAFT）聚合，制备了pH、温度和光三重敏感的含偶氮苯端基的聚甲基丙烯酸二甲氨基乙酯聚合物（PDMAEMA-AZO）。采用紫外光谱（UV）、红外光谱（FTIR）、核磁共振氢谱（1HNMR）和凝胶渗透色谱（GPC）对PDMAEMA-AZO的结构进行了表征，并考察了聚合物的光敏性、温敏性和pH敏感性。GPC结果表明，PDMAEMA-AZO的相对分子质量可控，且相对分子质量分布（PDI）小于1.78。PDMAEMA-AZO在不同溶剂中（氯仿、乙醇和水）的光敏性实验结果显示，该聚合物在氯仿、乙醇和水中均能够快速进行可逆光致顺反异构反应，在紫外与可见光的交替照射下，快速达到光稳态。PDMAEMA-AZO的温敏性实验表明，与聚甲基丙烯酸二甲氨基乙酯（PDMAEMA）相比，PDMAEMA-AZO的低临界溶解温度（LCST）更低。随着聚合物浓度的增加，其LCST降低，且相变窗口变窄。当pH超过9.44时，该聚合物的LCST保持不变，pH由9.44下降到7.34时，LCST升高，pH＜7.34时不再具有温敏性，说明该类聚合物是一种pH控制的具备LCST的温敏性聚合物。在紫外与可见光交替照射下，PDMAEMA-AZO 的LCST 表现为可逆的升高和降低，表明聚合物PDMAEMA-AZO具备光控温敏性。     

CO_2响应性双丙酮丙烯酰胺-co-乙烯胺温敏共聚物的制备及其相变行为

以双丙酮丙烯酰胺(DAAM)和N-乙烯基甲酰胺(NVF)为主要原料,过硫酸铵和亚硫酸氢钠为引发剂,通过水溶液自由基聚合反应制备了无规共聚物P(DAAM-co-NVF),并在碱性条件下水解得到共聚物P(DAAMco-VAm)。采用FTIR、~1HNMR、GPC和TGA对共聚物进行了表征,同时以UV-Vis和DSC对P(DAAM-co-NVF)和P(DAAM-co-VAm)水溶液的相转变行为进行研究。结果表明,共聚物P(DAAM-co-NVF)和P(DAAM-co-VAm)具有可调控的低临界溶解温度(LCST),通过改变共聚物组成和溶液质量分数可以调控P(DAAM-co-NVF)和P(DAAM-co-VAm)的LCST;在P(DAAM-co-VAm)水溶液中通入CO_2可以调控聚合物的LCST;P(DAAM-co-VAm)水溶液的LCST具有可逆的CO_2/N_2开关响应性。     

二步法制备CO2响应性DAAM-co-VAm温敏共聚物及其在水溶液中的相变行为

以双丙酮丙烯酰胺（DAAM）和N-乙烯基甲酰胺（NVF）为单体，以过硫酸铵和亚硫酸氢钠为引发剂进行水溶液自由基聚合，合成了共聚物P(DAAM-co-NVF)，并在碱性条件下水解制得了聚合物P(DAAM-co-VAm)。采用傅立叶红外光谱（FTIR）、核磁共振氢谱（1H-NMR）、凝胶渗透色谱（GPC）和热失重分析（TGA）对合成的产物进行了表征分析，同时以紫外可见光谱（UV-Vis）和差示扫描量热仪（DSC）对P(DAAM-co-NVF)和P(DAAM-co-VAm)水溶液的相转变行为进行了研究。结果表明，所制备的聚合物P(DAAM-co-NVF)和P(DAAM-co-VAm)具有可调控的低临界溶解温度（LCST），通过改变组成和聚合物溶液的浓度，可以调控P(DAAM-co-NVF)和P(DAAM-co-VAm)的LCST。而且，在P(DAAM-co-VAm)水溶液中通入CO2可以调控聚合物的LCST。P(DAAM-co-VAm)水溶液的LCST具有可逆的CO2/N2开关响应性能。     

温敏性微凝胶对蛋白质和酶的吸附性能

用微乳液聚合方法以N-异丙基丙烯酰胺为单体合成了温敏性微凝胶聚N-异丙基丙烯酰胺(PNIPAM),研究了其对两种蛋白质和两种酶的吸附性能,测定了吸附等温线和温度对吸附量的影响。结果表明,微凝胶在低临界溶解温度(LCST)附近吸附蛋白质和酶的量有一突跃,例如在LCST前后,1 g纳米颗粒吸附的酪蛋白的质量分别为225 mg和415 mg;吸附的枯草杆菌蛋白酶的质量分别为12 000U/mg和27 500 U/mg。蛋白质和酶是通过物理吸附作用结合到PNIPAM微凝胶上,可以用调节温度的方法,来控制温敏微凝胶对蛋白质和酶的吸附与脱附。     

种子乳液聚合制备MMA-DMAEMA共聚物及其表面活性研究

采用种子乳液聚合的方法制备了甲基丙烯酸甲酯(MMA)和甲基丙烯酸二甲胺基乙酯(DMAEMA)共聚物。分别以产物性状和黏度为考核指标,考察了引发剂种类、乳化剂种类、乳化剂用量和聚合温度对聚合产物的影响;合成了四种不同DMAEMA含量(DMAEMA含量均大于10%)的共聚物,并利用红外、核磁及元素分析对其结构进行了表征;研究了四种共聚产物的p H、温度敏感性及开关乳化性。实验结果表明:制备MMA-DMAEMA共聚物的最优实验条件为单体浓度为27%(其中种子乳液的单体MMA占5.4%)、引发剂用量为单体总质量2‰(种子乳液时用量为0.4‰)、V-50为引发剂、十二烷基三甲基溴化铵为乳化剂且用量占体系总质量的4.2%、反应温度为45℃;在碱性条件下,共聚物对温度敏感,具有低临界溶解温度(LCST),LCST随着溶液中Na OH浓度的增大而降低;随着单体配比中DMAEMA含量的增加,产物溶液表面张力增大,表面活性降低;MMA∶DMAEMA=1∶1或2∶1时,共聚产物具有开关乳化性,为其在含油污泥方面的应用奠定了基础。     

Antimicrobial and Thermal-Responsive Layer-by-Layer Assembly Based on Ionic-Modified Guanidine Polymer and PVA

Summary  Water-soluble polymers, cationic polyhexamethylene guanidine hydrochloride (CPHGH) with antimicrobial property and acetalyzed poly(vinyl alcohol)/sodium acrylate (APVA-co-AANa) with temperature-responsive property were synthesized, and used as cationic and anionic polymer respectively to assemble multilayers to attempt to obtain a unique antimicrobial polymer system via the technique of layer by layer (LbL) assembly. The measurement of turbidity change for APVA-co-AANa aqueous solution under different temperatures revealed that the lower critical solution temperature (LCST) of APVA-co-AANa can be tailored by controlling the degrees of acetalysis (DA). Lower LCSTs were observed for the APVA-co-AANa with a higher DA. AFM images reveal that the particles on the surface of (CPHGH/APVA-co-AANa) and (PDADMAC/APVA-co-AANa) multilayers became larger after the material was treated at 60 C; while the roughness of the surfaces was increased as the layer number increase and then decrease. Moreover, antimicrobial test also proved that cellulose fiber assembled with (CPHGH/APVA-co-AANa) multilayers exhibited higher antimicrobial activity against coliform and staphylococcus aureus.     

Synthesis and characterization of temperature‐responsive poly(vinyl alcohol)‐based copolymers

A poly(vinyl alcohol) (PVA)/sodium acrylate (AANa) copolymer was synthesized to improve the water solubility of PVA at the ambient temperature. Furthermore, a series of temperature‐responsive acetalyzed poly(vinyl alcohol) (APVA)‐co‐AANa samples of various chain lengths, degrees of acetalysis (DAs), and comonomer contents were prepared via an acid‐catalysis process. Fourier transform infrared and ¹H‐NMR techniques were used to analyze the compositions of the copolymers. The measurement of the turbidity change for APVA‐co‐AANa aqueous solutions at different temperatures revealed that the lower critical solution temperature (LCST) of the copolymers could be tailored through the control of the molecular weight of the starting PVA‐co‐AANa, DA, and comonomer ratios. Lower LCSTs were observed for APVA‐co‐AANa with a longer chain length, a higher DA, and fewer acrylic acid segments. In addition, the LCSTs of the APVA‐co‐AANa aqueous solutions appeared to be salt‐sensitive. The LCSTs decreased as the concentration of NaCl increased. Moreover, atomic force microscopy images of APVA‐co‐AANa around the LCST also proved the temperature sensitivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚(甲基丙烯酸N,N-二甲氨基乙酯/丙烯酸2-乙基己酯)的温度及pH敏感性能的研究

采用紫外光引发光聚合得到了聚甲基丙烯酸N ,N 二甲氨基乙酯〔P(DMAEMA)〕均聚物和不同组成的聚甲基丙烯酸N ,N 二甲氨基乙酯 /丙烯酸 2 乙基己酯〔P(DMAEMA/EHA)〕共聚物。傅立叶红外光谱和核磁共振氢谱测定了P(DMAEMA/EHA)共聚物的链结构 ,结果表明 :聚合的投料比与所得产物的实际组成比一致。在 pH >8,P(DMAEMA/EHA)共聚物溶液的低临界溶液温度 (LCST)随聚合物中EHA组分的增加逐渐下降 ;在pH≤ 8时 ,则观测不到体系的LCST。 37℃下均聚物及共聚物试样 (D、D/E1、D/E2、D/E3)的pH敏感点分别为8 80 ,8 72 ,8 37,8 2 9。共聚物结构中EHA组分越多 ,则 pH敏感点越低。P(DMAEMA)均聚和共聚物的LCST随着NaCl浓度的升高而线性下降 ,且下降的速率相等。     

Temperature sensitive polymers based on 2-(dimethyl maleinimido)-N-ethyl-acrylamide: Copolymers with N-isopropylacrylamide

Summary Temperature sensitive polymers with pendant dimethyl maleinimide side groups were prepared by the copolymerization of N-isopropylacrylamide (NIPAAm) with varying amounts of a functional N-substituted acrylamide (2-(dimethyl maleinimido)-N-ethyl-acrylamide, DMIAAm). The polymers were characterized by ¹H-NMR, IR, DSC and TGA. Their relative reactivity ratios have been determined. Aqueous solutions of the copolymers showed lower critical solution temperature behaviour (LCST). The phase transition temperatures of the aqueous solutions of these copolymers decreased with increasing comonomer content and disappeared at DMIAAm contents at or above 15.9 mol-%. Received: 13 September 1999/Accepted: 7 March 2000     

Thermoreversible swelling behaviour of hydrogels based on N-isopropylacrylamide with a hydrophobic comonomer

Hydrogels were prepared by free radical polymerisation in aqueous solution of N-isopropylacrylamide (NIPA) and of NIPA with di-n-propylacrylamide (DPAM), di-n-octylacrylamide (DOAM) or di-dodecylacrylamide (DDAM) as hydrophobic comonomer. N,N-methylene bisacrylamide (BIS) and glyoxal bis(diallyacetal) (GLY) were used as crosslinkers. A series of copolymers with three different comonomer contents was synthesised and for some polymers three different crosslinker concentrations were employed. The swelling equilibrium of these hydrogels was studied as a function of temperature, hydrophobic comonomer species and content in aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS). In pure water the gels showed a discontinuous volume phase transition at 33 and 30 °C for PNIPA and hydrophobically modified PNIPA copolymeric hydrogels, respectively. The swelling ratio r and the transition temperature (LCST) increased at low temperatures with the addition of SDS, this is ascribed to the conversion of non-ionic PNIPA gels into polyelectrolyte gels through the binding of SDS. At SDS concentration below 0.5 wt%, gels exhibited a single discontinuous volume transition at 36-38 °C. However, for SDS concentration above 0.5 wt%, two discontinuous volume transitions at 36-40 and 70 °C were observed. Additionally, the replacement of BIS by the novel octafunctional crosslinker glyoxal bis(diallylacetal) (GLY) yielded an increase in the swelling ratio.     

聚(丙烯酸-共聚-苯并-18-冠醚-6-丙烯酰胺)的铯离子响应特性及其铯离子检测性能

制备了一种聚(丙烯酸-共聚-苯并-18-冠醚-6-丙烯酰胺)（PAB）线形共聚物,并系统研究了不同丙烯酸含量的PAB线形共聚物对铯离子的响应特性及其用于铯离子浓度检测的性能。结果表明,在不同浓度的铯离子溶液中,PAB线形共聚物的低临界溶解温度（LCST）会随着铯离子浓度增加向低温迁移;在实验范围内,当PAB线形共聚物中的丙烯酸质量分数为30%时,其铯离子响应特性最有利于水溶液中铯离子浓度的检测。通过系统实验研究,确立了PAB共聚物的LCST与水溶液中铯离子浓度的关系函数;利用该关系函数,可简单地通过测定未知铯离子浓度的PAB溶液LCST,即可推断出该溶液中的铯离子浓度。该研究为铯离子的便捷检测提供了新手段。     

Effect of intermolecular and intramolecular forces on hydrodynamic diameters of poly(N‐isopropylacrylamide) copolymers in aqueous solutions

A novel copolymer, poly(N‐isopropylacrylamide‐co‐hydroxypropyl methacrylate‐co‐3‐trimethoxysilypropyl methacrylate) has been synthesized and the hydrodynamic diameters in various aqueous solutions under different temperatures are determined by dynamic light scattering. The results show that the hydrodynamic diameters of copolymers have no obvious change in each working solution below lower critical solution temperature (LCST); across LCST, the diameters increased suddenly at different initial temperature in various aqueous solutions; above LCST, they decreased slightly as the temperature increased in UHQ water, and increased continuously with increasing temperature or salt concentration in saline solutions, and reduced with the rising of pH value in pH buffer. These are attributed to different intermolecular and intramolecular forces leading to disparity in dimension, conformation, and LCST of copolymers. The hydrogen bonding between water molecules and copolymer chains could maintain size and conformation of copolymer single chain; the hydrogen bonding between amide linkages and hydrophobic interactions between isopropyl groups result in intramolecular collapse and intermolecular aggregation; the electrostatic repulsion weakens aggregation extent of copolymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Simultaneous multiple sample light scattering detection of LCST during copolymer synthesis

This work has two objectives in the investigation of polymer solution lower critical solution temperature (LCST): First, to develop a new instrument to monitor LCST onset during copolymer synthesis by coupling several thermostatted light scattering flow cells to the output stream of an ACOMP system (Automatic Continuous Online Monitoring of Polymerization reactions). Second, to use this to investigate effects on LCST when N-isopropylacrylamide (NIPAM) is copolymerized with a charged comonomer, styrene sulfonate (SS). This comonomer pair has widely separated reactivity ratios. SS is rapidly consumed, yielding composition drift toward NIPAM rich polymer. High content SS chains inhibited LCST, and SS was dramatically effective at suppressing LCST down to copolymers of 5% molar SS in 10 mM NaCl aqueous solvent. LCST for higher content SS chains was elevated and required significant additional ionic strength to occur. It was determined that the suppression of the LCST by SS is chiefly an intramolecular effect.     

Thermoresponsive sodium alginate‐g‐poly(N‐isopropylacrylamide) copolymers III. Solution properties

Stimuli‐responsive biocompatible and biodegradable materials can be obtained by combining polysaccharides with polymers exhibiting lower critical solution temperature (LCST) phase behavior, such as poly(N‐isopropylacrylamide) (PNIPAAm). The behavior of aqueous solutions of sodium alginate (NaAl) grafted with PNIPAAm (NaAl‐g‐PNIPAAm) copolymers as a function of composition and temperature is presented. The products obtained exhibit a remarkable thermothickening behavior in aqueous solutions if the degree of grafting, the concentration, and the temperature are higher than some critical values. The sol–gel‐phase transition temperatures have been determined. It was found that at temperatures below LCST the systems behave like a solution, whereas at temperatures above LCST, the solutions behave like a stiff gel, because of PNIPAAm segregation. This behavior is reversible and could find applications in tissue engineering and drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Analysis of polyolefins and olefin copolymers using Crystaf technique: Resolution of Crystaf curves

An experimental technique, crystallization analysis fractionation (Crystaf), is used to analyze compositional uniformity of ethylene/α‐olefin copolymers and isotactic polypropylene. A computerized method for quantifying Crystaf data is developed based on resolution of Crystaf curves into their elemental components, with each component representing a fraction of the polymer with the same degree of chain imperfection. This analysis of Crystaf curves gives three parameters characterizing crystallizable polymer material: (a) the number of compositionally uniform components, (b) properties of each compositionally uniform component (in the case of ethylene/α‐olefin copolymers, the comonomer content), and (c) the quantity of each component. Crystaf analysis of several ethylene/1‐hexene copolymers produced with supported Ti‐based Ziegler‐Natta catalysts shows the existence of two groups of copolymer components. The first group includes components with low comonomer content, in the Crystaf analysis they precipitate at high temperatures as several relatively sharp peaks. The second group includes components with high comonomer contents; they precipitate at much lower temperatures, as a broad overlapping group of peaks. The peak resolution technique was applied to analysis of ethylene/α‐olefin copolymers prepared with a supported catalyst at different temperatures, a copolymer produced with a pseudo‐homogenous Ziegler‐Natta catalyst, and to isotactic polypropylene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007