PMAA纳米水凝胶的水相制备

利用表面活性剂间的疏水作用以及表面活性剂与单体间的氢键作用,促使甲基丙烯酸(MAA)单体在原位生成的聚甲基丙烯酸甲酯(PMMA)种子乳胶表面的选择性聚合,实现了PMAA纳米水凝胶的水相"绿色"制备。利用动态光散射、傅里叶红外光谱、透射电子显微镜表征了PMAA纳米水凝胶的尺寸、组成、形貌和pH响应性。研究了聚氧乙烯失水山梨醇单月桂酸酯(吐温20)的用量、N,N’-亚甲基双丙烯酰胺(MBA)的用量、MAA的用量和加入方式、十二烷基硫酸钠(SDS)的补加速率等对PMAA纳米水凝胶的尺寸和溶胀性能的影响。结果表明:PMAA纳米水凝胶为核-壳结构;随着MBA用量的减小、吐温20用量的增加、MAA用量的增加,PMAA纳米水凝胶的尺寸和溶胀比均增大;当采用半连续加入MAA时,PMAA纳米水凝胶的尺寸和溶胀比变小;当SDS的补加时间由60min延长到100min时,PMAA纳米水凝胶的尺寸逐渐变小。PMAA纳米水凝胶具有良好的pH响应性,当介质的pH从1增加到6时,其流体力学体积扩张了64倍。     

聚甲基丙烯酸纳米水凝胶的水相合成及其磁性功能化

利用十二烷基硫酸钠/吐温20复配表面活性剂和原位生成的聚甲基丙烯酸甲酯(PMMA)种子乳胶,发展了一种可在全水相中"绿色"合成较高浓度的聚甲基丙烯酸(PMAA)纳米水凝胶的新方法.以PMAA纳米水凝胶为前驱体,采用原位氧化沉淀法制备了磁性PMAA纳米微球.利用动态光散射法、FTIR分析、TEM观察、振动样品磁强计测试(VSM)、热重分析(TG)等对纳米水凝胶和磁性微球进行了表征,并探讨了PMAA纳米水凝胶的形成机理.结果表明,吐温20与MAA和PMAA间的氢键作用,促成了交联PMAA/吐温20复合物层在PMMA种子乳胶表面的选择性生长,导致生成了具有核壳结构的PMAA纳米水凝胶.PMAA纳米水凝胶表现出良好的p H响应性,当介质的p H值由1增加至6时,其流体力学体积扩张了近50倍.磁性PMAA纳米微球具有超顺磁性,其饱和磁化强度高达50 A·m~2/kg.     

甲基丙烯酸在生物相容性微球CPVA表面的引发接枝聚合

交联聚乙烯醇（CPVA）微球表面含有大量的羟基,具有良好的生物相容性。在水溶液体系中利用这些羟基,与铈盐构成氧化还原引发体系,实施了甲基丙烯酸（MAA）的表面引发接枝聚合,制备了接枝微球CPVA—g—PMAA,考察了主要因素对接枝聚合的影响。采用红外光谱（FT—IR）及扫描电子显微镜（SEM）对接枝微球进行了表征。结果表明,羟基-铈盐氧化还原引发体系可有效地引发MAA在CPVA微球的表面接枝聚合,当铈盐浓度为4．9×101mol／L、硫酸浓度为0．17mol／L、反应温度为45。C、单体浓度为0．54mol／L时,每1。0g接枝微球CPVA—g—PMAA可接枝PMAA30g。     

聚甲基丙烯酸基纳米水凝胶的“绿色”合成

利用原位生成的聚甲基丙烯酸甲酯种子乳胶模板以及表面活性剂与功能单体间的正负电荷作用,发展了一种可在全水相中“绿色”合成聚甲基丙烯酸(PMAA)基纳米水凝胶的新方法.利用动态光散射法、ξ-电位测定、FTIR和TEM对纳米水凝胶的尺寸及其分布、表面电荷、组成、形态、结构和pH响应行为进行了表征.结果表明,PMAA基纳米水凝胶具有聚甲基丙烯酸甲酯内核和交联聚甲基丙烯酸外壳的核壳结构.当甲基丙烯酸(MAA)的用量由2 mL增至3 mL时,PMAA基纳米水凝胶的尺寸变大.当MAA的用量增加至5 mL时,反应体系中除了生成PMAA基纳米水凝胶外,还生成了PMAA次级粒子.PMAA基纳米水凝胶表现出良好的pH响应性:当介质的pH值由2增加至7时,其流体力学体积扩张了近80倍.     

P(DEAM-co-MAA)在稀水溶液中构象行为的荧光探针研究

利用UV透光率测定,荧光探针技术等研究了N,N-二乙基丙烯酰胺(DEAM)与甲基丙烯酸(MAA)的共聚物P(DEAM-co-MAA) 在稀水溶液中的构象行为.结果表明，当共聚物中DEAM含量小于8.00％(molar fraction),溶液的pH < 6时,P(DEAM-co-MAA)在稀水溶液中的构象行为与聚甲基丙烯酸(PMAA)相似,共聚物可形成疏水微区,表现为一种较为高度压缩的线团构象;当共聚物中DEAM含量大于8.00％(molar fraction)时,由于高分子的稀释效应,P(DEAM-co-MAA)在pH 2～10范围内表现为较为松散的伸展构象.P(DEAM-co-MAA)构象随其组成和pH变化的这种性质有可能在新型敏感性凝胶的合成设计上获得应用.     

高性能胰蛋白酶分子表面印迹材料的制备及其大分子识别特性研究

以交联聚乙烯醇(CPVA)微球为基质,以甲基丙烯酸(MAA)为功能单体,在中性水介质中制备了高性能胰蛋白酶(TRY)大分子表面印迹材料。首先通过CPVA微球表面的羟基与甲基丙烯酰氯之间的酯化反应,将大量可聚合双键甲基丙烯酰基(MAO)引入微球表面,获得改性微球MAO-CPVA。在中性水溶液中,单体MAA的羧基几乎发生完全电离,凭借强烈的静电相互作用,MAA自动结合在碱性蛋白TRY大分子周围,形成单体-模板复合体。水溶液中过硫酸铵/亚硫酸氢钠引发体系所产生的自由剂,使包围在TRY周围的单体MAA与交联剂N,N'-亚甲基双丙烯酰胺(MBA)在微球MAO-CPVA表面发生接枝交联聚合,而模板TRY则被包裹在交联网络之中,除去模板后便得到了TRY表面印迹微球MIP-PMAA/CPVA。深入考察了该表面印迹微球的大分子识别性能。研究结果表明,表面印迹微球MIP-PMAA/CPVA对TRY具有优良的结合亲和性,结合容量高达84mg·g~(-1)(3.6μmol·g~(-1));对模板蛋白TRY具有特异的识别选择性,相对于另一种碱性蛋白木瓜蛋白酶,印迹微球对TRY的选择性系数高达21.62。     

卵清蛋白与离子型表面活性剂的相互作用

本文通过荧光光谱法、紫外-可见吸收光谱法和透射电镜并结合电导率测定分别研究了水中卵清蛋白与阴离子表面活性剂十二烷基硫酸钠（SDS）和阳离子表面活性剂十二烷基三甲基溴化铵（DTAB）和十六烷基三甲基溴化铵（CTAB）之间的相互作用。研究结果表明卵清蛋白可以增加SDS和CTAB的临界胶束浓度,但对DTAB的临界胶束浓度没有影响。阴离子表面活性剂可以使卵清蛋白构象完全伸展,而阳离子表面活性剂却不具备此种作用。表面活性剂单体与卵清蛋白的相互作用强于表面活性剂胶束与卵清蛋白的相互作用。     

含氟丙烯酸酯共聚乳液及其膜表面特性的研究

以十二烷基硫酸钠 (SDS)和OP 10混合乳化剂 ,制备了甲基丙烯酸全氟辛基乙酯 (FMA8) 甲基丙烯酸丁酯 (BMA) 甲基丙烯酸 (MAA)共聚乳液 .通过DSC、FT IR、1 H NMR对共聚物的结构、组成进行了表征研究 .采用JZHY 180界面张力仪研究了共聚乳液膜表面的性质 ,结果表明 ,随着共聚物中全氟单体含量的增加 ,共聚物膜的表面能显著降低 ,当全氟单体的含量达到 2 5wt %时 ,其表面能降低到 19 74mJ m2 .X ray光电子能谱(XPS)对共聚物表面原子组成的分析结果表明 ,共聚物表面氟的含量远高于其平均含量 ,证明了含氟基团的趋表现象 .经退火处理 ,共聚物膜表面的氟含量增加 ,表面自由能降低     

微乳液法制备水溶性双亲丙烯酰胺-苯乙烯嵌段共聚物

分别以十二烷基硫酸钠 (SDS)、壬基酚聚氧乙烯醚 (OP 10 )为表面活性剂 ,丙烯酰胺 (AM)的水溶液为连续相 ,苯乙烯 (St)为分散相 ,构成微乳液共聚合体系 ,合成了水溶性双亲嵌段共聚物 ,并通过荧光探针技术、差示扫描量热 (DSC)测试及流变性能的测定表征了共聚物的嵌段性结构 ,用红外光谱 (FTIR)及紫外光谱 (UV)分析了共聚物的化学组成     

稀水溶液中聚乙烯吡咯烷酮构象行为的荧光研究

以苊烯(ACE)为荧光标记物,8-苯胺基-萘磺酸(ANS)为荧光探针,利用荧光各向异性、荧光猝灭以及非辐射能量转移等静态荧光技术研究了聚乙烯吡咯烷酮(PVP)在稀水溶液中的构象行为.结果表明,PVP在稀水溶液中呈松散自由线团构象,这种构象不随溶液pH的变化而显著变化.不同于其它水溶性高分子,PVP有很强的氢键形成能力,易与具有活泼氢的其它高分子或小分子相结合,并易被金属氧化物类吸附剂吸附.因此PVP可被用来修饰某些具有疏水结构的水溶性高分子.PVP水溶液在pH=7以上相当稳定,放置1周性质没有显著变化.     

Photophysics of carbazole-containing systems. 1. Dilute solution behavior of poly(N-vinyl carbazole) and N-vinyl carbazole/methyl acrylate copolymers

Steady-state and time-resolved fluorescence techniques have been used to study the photophysical behaviors of poly(N-vinyl carbazole), PNVCz and a series of N-vinyl carbazole-methyl acrylate (NVCz-co-MA) copolymers in dilute solution as a function of both NVCz composition and temperature. A kinetic scheme, intended to describe intramolecular excimer formation across the entire NVCz composition range, is proposed. In low aromatic content copolymers, two monomer species (unquenched and quenched monomer) and two excimer species (the sandwich-like excimer and a higher energy excimer) exist. The contribution from monomer emission to the overall fluorescence decreases with increasing NVCz content through increased excimer formation: this is likely to be consequent upon (1) an increase in the number of excimer forming sites, and (2) increasing efficiency of energy transfer from the excited monomers to the excimer forming sites. In the homopolymer, PNVCz, the only emission that can be observed on a nanosecond timescale is excimeric. This fluorescence appears to originate from three excimer species (the sandwich-like excimer, and two higher energy forms). For the homopolymer, the current observations are consistent with the model proposed by Vandendriessche and De Schryver [Polym. Photochem. 7 , 153 (1986)]. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 963–978, 1997     

Temperature-driven Precipitation of poly(N-isopropylacrylamide-co-methacrylic acid) in Cationic,Anionic and Nonionic Surfactant Solutions

The temperature-driven precipitation of poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) in anionic, cationic, and non-ionic surfactants solutions was investigated under an acidic (e.g. pH 3.0) and an alkali condition (pH 9.0). Under the acidic condition, sodium dodecyl sulfate (SDS, anionic) and cetyltrimethylammonium chloride (CTAC, cationic) increased the cloud point of the copolymer and they suppressed the temperature-sensitivity. Under the alkali condition, SDS suppressed the temperature sensitivity as under the acidic condition, but CTAC boosted the temperature sensitivity and it decreased the cloud point of the copolymer. The effect of CTAC on the phase transition under the alkali condition was opposite to the effect observed under the acidic condition. Tween 20 (non-ionic) had little effect on the cloud point and the temperature-sensitivity under both the acidic and the alkali conditions.     

Aggregation of ionic surfactants to block copolymer assemblies: a simple fluorescence spectral study

A simple and elegant method based on steady-state fluorescence spectral measurement is demonstrated to study the interaction mechanism of copolymers and ionic surfactants with a suitable selection of fluorescent probe and also its general applicability in studying other systems. Three different concentration regions have been indicated from the changes in full width at half-maximum of the emission spectra and fluorescence intensity of coumarin 153 with the molar ratio of ionic surfactant to triblock copolymer (n). At low n values, copolymer-surfactant complexes are basically copolymer-rich micelles with few surfactant molecules, and at very high n values, copolymer-rich micelles are destroyed and surfactant-rich micelles with free copolymer monomers are formed. It has been observed that, in the intermediate surfactant concentration region, the transformation of a dominantly copolymer-rich complex to a mainly surfactant-rich complex can be either gradual incorporation of surfactants into the copolymer-rich micelles with freeing of copolymer units until surfactant-rich micelles are formed (type I) or simultaneous buildup of surfactant-rich micelles together with the destruction of copolymer-rich micelles (type II). The interaction mechanism for nonionic copolymers (P123 and F127) with ionic surfactants (SDS and CTAC) is mainly type II, but at higher copolymer concentrations interaction via the type I mechanism also operates. However, it is dominantly the type I mechanism that operates for common nonionic (TX100) and ionic surfactants.     

温度/pH敏感性P(MAA-g-DEAM)共聚物水溶液的相行为

利用大分子单体技术通过自由基共聚法合成了由甲基丙烯酸(MAA)和N, N-二乙基丙烯酰胺(DEAM)组成的几种不同组成的P(MAA-g-DEAM)接枝共聚物.通过UV-Vis 透光率的测定和荧光探针技术, 对共聚物水溶液的相行为进行了研究. 研究表明, 此接枝共聚物具有相互独立的温度和pH 敏感性；几种组成不同的P(MAA-g-DEAM)接枝共聚物具有基本相同的低临界溶解温度(LCST)；它们的临界相变pH与接枝共聚物的组成有关, 温敏性PDEAM 枝链的接枝率越高, 其临界相变pH 越高. pH > 5.5 时, 接枝共聚物的主链是一种较为松散的线团构象；pH < 5.5 时, 接枝共聚物的主链是一种较为压缩的线团构象. 这种接枝共聚物高分子聚集体在新的纳米复合材料的合成方面有可能获得应用.     

Effects of pH,salt, surfactant and composition on phase transition of poly(NIPAm/MAA) nanoparticles

The volume phase transition of poly(NIPAm/MAA) copolymer nanoparticles in buffer solutions at various pH and in aqueous solutions of KCl or ionic surfactants (SDS and DTMAB) was systematically studied using dynamic laser scattering technique. It was found that ionizable MAA groups imparted a responsiveness of the particles to pH and electrolytes. At pH > pKa of the copolymer, electrostatic repulsion of negative charges, mostly from COO⁻ groups, was a governing mechanism for preventing the particles from collapse at T > T_tr. The particles exhibited a sharp volume phase transition upon elimination of the negative charges by decreasing the pH of the medium or by the addition of cationic surfactant. At pH < pKa, the presence of MAA groups enhanced the hydrophobicity of the particles as indicated by a lower T_tr and a sharper volume phase transition. A pH 4 buffer at the same ionic strength exhibited the most significant effect on the particle size and phase transition, followed by the ionic surfactant with an opposite charge (e.g., DTMAB), KCl, and finally the ionic surfactant with the same charge (e.g. SDS). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2667–2676, 1999     

含苯胺低聚物侧链的导电共聚物的合成与性能研究

通过高分子反应合成了含有不同长度苯胺链段的聚甲基丙烯酸类接枝聚合物 ,研究结果发现 ,当苯胺链段达到一定长度时 ,经质子酸掺杂后的聚合物具有一定的电导性 ,其中 ,接枝苯胺八聚体的共聚物经质子酸掺杂后其电导率可以达到 10 - 5S cm .     

Study of pH-sensitive copolymer/phospholipid complexes using the langmuir balance technique: effect of anchoring sequence and copolymer molecular weight

The behavior of three copolymers of N-isopropylacrylamide (NIPAM), methacrylic acid (MAA), and hydrophobic moiety was studied at phospholipid monolayer/subphase interfaces. The hydrophobic moieties, N-terminal dioctadecylamine (DODA) and random octadecylacrylate (ODA), were used as anchoring groups. The interactions between a 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC) monolayer and the copolymers were studied using the Langmuir balance technique. The effect of subphase pH, distribution of anchors along the copolymer chain, and copolymer molecular weight on the nature of the interactions between the copolymer chains and the DSPC monolayer were investigated. A first-order kinetics model was used to analyze the copolymers adsorption at the DSPC monolayer/subphase interface and allowed the interaction area between the copolymer chains and the DSPC monolayer, A(x), to be determined. The interaction area appears to depend on the subphase pH and the copolymer molecular weight. On decreasing pH, the interaction area of high molecular weight copolymers increases significantly; this is consistent with the copolymer chain phase transition from an extended coil to a collapsed globule while pH is lowered. In the latter conformation, strong hydrophobic attractive interactions between the copolymer chains and the hydrophobic part of the DSPC monolayer favor the copolymer intercalation, which could eventually provoke the phospholipidic layer destabilization or rupture.     

Preparation and Characterization of Poly(N‐Vinylpyrrolidone‐co‐Methacrylic Acid) Hydrogels

In this study, N‐vinylpyrrolidone (VP)/methacrylic acid (MAA) copolymers have been prepared at three different mole percents, the methacrylic acid composition being around 5, 10, 15%. MAA and VP monomer mixtures have been irradiated in ⁶⁰Co‐γ source at different irradiation doses and percent conversions have been determined gravimetrically. ～80% conversion of monomers into hydrogels were performed at 3.4 kGy irradiation dose. These hydrogels were swollen in distilled water at pH 4.0, 7.0, and 9.0. P(VP/MAA) hydrogel which contains 5% methacrylic acid showed the maximum % swelling at pH 9.0 in water. Diffusion of water was found to be of non‐Fickian character. Diffusion coefficients of water in P(VP/MAA) hydrogels were calculated. Initial swelling rates of P(VP/MAA) hydrogels increased with increasing pH and MAA content in hydrogels. Swelling kinetics of P(VP/MAA) hydrogels was found to be of second order. Thermal behavior of PMAA, PVP and P(VP/MAA) hydrogel were investigated by thermal analysis. P(VP/MAA) hydrogel gained new thermal properties and the temperature for maximum weight loss and temperature for half‐life of P(VP/MAA) hydrogel were determined.     

Charges of soluble amphiphiles and particles: random and diblock copolymerizations of MAA/AAm,MAA/St,and MAA/4VP in ethanol

Random and reversible addition-fragmentation chain transfer (RAFT) copolymerizations of methacrylic acid (MAA)/acrylamide (AAm), MAA/styrene (St), and MAA/4-vinyl pyridine (4VP) were carried out in ethanol. (CPDB)-terminated PMAA (PMAA-CPDB) and 2,2′-azobis(2,4-diemthylvaleronitrile) (V-65) was used as the macromolecular chain transfer agent (CTA) and initiator, respectively. Electric conductivity of copolymerization systems was traced throughout the polymerizations, and charges of soluble copolymer and particles were detected. As a result, a considerable increase of conductivity was observed in all of the RAFT polymerization systems, whereas the variation of conductivity in the random copolymerization systems was insignificant. The high conductivity of RAFT polymerization was dominantly contributed by the soluble diblock copolymers in the serum, rather than their particles, except for P(MAA-b-4VP) where only the particles was obtained due to the zwitterionic interactions of PMAA segments and 4VP. In the direct current (DC) field, the behavior of these soluble diblock copolymers, P(MAA-b-AAM) and P(MAA-b-St), indicated that they were positively charged, whereas the particles of (PMAA-b-AAm) and P(MAA-b-4VP) were surprisingly negatively charged, though the composition of MAA was dominant. Soluble random copolymers of P(MAA-co-St) and P(MAA-co-4VP) represented the charge neutrality. These results indicated that the positive charges were contributed by the solvophobic block in the soluble diblock copolymers. Therefore, the diblock copolymers were the macrodipoles boosting the conductivity of solution. Meanwhile, it indicated that the electrostatic interactions of dipoles were possibly the main driving force of their self-assembly. Generally, compared with RAFT polymerization, the particles were hard to be prepared in the random copolymerization. It implies that the electrostatic interactions of diblock copolymers also played an important role in the particle formation.