羟丙基甲基纤维素的流变性质及热凝胶化行为

应用旋转黏度仪测试了四种羟丙基甲基纤维素(HPMC)溶液样品在不同浓度下的流变性质,并用动态旋转流变仪研究了HPMC样品的热凝胶效应。结果表明,HPMC的相对分子质量对流变性质有显著影响,而取代基的影响不很明显;同时得出了流体行为指数与浓度之间的数学模型关系式。取代基对热凝胶效应影响显著,而对不同取代度的样品系列而言,相对分子质量的影响趋势各不相同。     

温度和pH值对智能水凝胶溶胀行为的影响

以N-马来酰化壳聚糖(N-MACH)为交联剂,N-异丙基丙烯酰胺(NIPAAm)为单体,羧甲基纤维素钠(CMC)为半互穿材料,分别合成了PNIPAAm和PNIPAAm/CMC半互穿网络智能水凝胶,研究了两种水凝胶在不同温度的去离子水和不同pH值的缓冲溶液中的溶胀现象,结果表明介质温度和pH值对水凝胶的溶胀行为有显著影响。在温度和pH值一定时,水凝胶的溶胀率随着交联剂用量的增加而下降,随着CMC用量的增加而上升。     

丙烯酰胺类共聚物水凝胶的合成及性能研究

用自由基聚合法合成了不同摩尔配比的HEMA／AM共聚物水凝胶材料。研究了单体组成、温度、pH值、离子强度等因素对凝胶溶胀性能的影响。结果表明：水凝胶的溶胀速度较快;水凝胶在pH值小于4及pH值大于9的酸、碱溶液中发生水解,导致水凝胶的饱和含水量大幅增加,而在弱酸性溶液中几乎没有变化;水凝胶的饱和含水量对离子强度的变化不够敏感;随着温度的升高水凝胶的饱和含水量略有减少,说明此类水凝胶对温度的敏感性也较弱。     

聚乙烯醇-壳聚糖复合水凝胶的溶胀性能

以聚乙烯醇(PVA)和壳聚糖为原料、以戊二醛为交联剂,在醋酸溶液中合成了聚乙烯醇-壳聚糖复合水凝胶,研究了影响水凝胶溶胀性能的多种因素,实验结果表明,该凝胶对pH、离子、温度敏感,且在pH=3.13盐酸溶液、常温下的蒸馏水及8℃蒸馏水中溶胀度较大,分别为1 112.2%、974.2%、1 036.8%,凝胶溶胀度随着干燥温度及干燥时间的增加而减小,聚乙烯醇种类对水凝胶溶胀性能有显著影响,PVA-1788与壳聚糖形成的水凝胶溶胀度最大为2 074.1%。聚乙烯醇-壳聚糖复合水凝胶因具有优良的机械强度、生物相容性及生物降解性,同时又具有pH/离子/温度敏感性,因此日益显示其在生物医学材料等领域的重要性。     

温度和pH双重刺激响应型水凝胶的溶胀性能研究

以丙烯酰胺、丙烯酸和双丙酮丙烯酰胺为原料,以N,N'-亚甲基双丙烯酰胺为交联剂,2-酮戊二酸为引发剂,采用光引发聚合方法制备出系列新型温度和pH响应型水凝胶。考察了交联剂用量、水凝胶组成、温度和pH值对凝胶溶胀性能的影响。结果表明,随交联剂用量的增加,凝胶的溶胀率减小,随凝胶组成中AA含量的增加,凝胶的溶胀率增加。凝胶的溶胀率随温度的升高而减小,随pH值的增大而增加,表现出显著的温敏和pH敏感性。     

聚甲基丙烯酸N,N-二甲基氨基乙酯水凝胶敏感性研究

采用热化学聚合法制备了聚甲基丙烯酸N,N-二甲基氨基乙酯(PDMAEMA)水凝胶,对其溶胀性能进行了研究,考察了温度、pH和离子强度对其溶胀行为的影响.结果表明,PDMAEMA水凝胶具有温度敏感性,其低临界相变温度在50℃左右;水凝胶具有pH敏感性,其溶胀率在pH=8附近有一突变的下降过程;具有离子强度敏感性,溶胀率随离子强度的增加呈线性下降的趋势.     

天然高分子亲水性凝胶材料在竹醋液中 溶胀度的初步研究

测定了壳聚糖、黄原胶、海藻酸钠3种天然高分子亲水性凝胶材料在竹醋液中的溶胀度。探讨了温度、pH值对其溶胀度和溶胀速率的影响。结果表明在20~40℃ 范围内,3种凝胶的溶胀度和溶胀速率随着温度的升高而增加;在不同pH值的竹醋液中,壳聚糖和黄原胶的溶胀速率十分相近,而且黄原胶比壳聚糖更稳定。     

生物温敏性水凝胶的研究

采用明胶（Gel）和N－异丙基丙烯酰胺（NIPAM）为原料，制备交联结构不同的Gel-PNIPAM水凝胶，研究不同的pH值、温度对它们的溶胀度和溶胀速度的影响，进而了解明胶的交联结构对水凝胶的温敏性、pH敏感性的影响。结果表明：不同交联结构的Gel-PNIPAM水凝胶对pH值的响应取决于明胶部分，Gelx-PNIPAM水凝胶的温敏性最明显，温度大于LCST（最低临界溶液温度），Gel-PNIPAMx与Gelx-PNIPAMx,Gelx-PNIPAM相比，呈现更高的溶胀度及溶胀速度，其控制过程分别符合Case-Ⅱ和Fick定律。     

NVP接枝壳聚糖水凝胶的合成与溶胀性能

合成了N-乙烯基吡咯烷酮（NVP）接枝壳聚糖（CHI）水凝胶,讨论了NVP/CHI、引发剂、交联剂、聚合温度、乙酸浓度等因素对接枝率及凝胶溶胀性能的影响,NVP∶CHI为6时,接枝率达到300%以上. 溶胀温度、pH值、盐浓度等对凝胶溶胀性能的影响实验表明,凝胶表现出温度敏感性,在40 ℃出现最大平衡溶胀率,并观察到一级相转变;在中性或弱酸性介质中溶胀性能较好;与PVP凝胶相比,NVP接枝CHI凝胶表现出反聚电解质效应. 溶胀动力学研究表明,在溶胀前期,CHI含量较高时,凝胶趋向于非Fick溶胀,说明除了溶剂扩散外,凝胶网络链段弛豫、水分子与凝胶网络间及凝胶高分子链段间相互作用对凝胶溶胀性能的影响至关重要;CHI含量较高时则趋向于Fick溶胀.     

丙烯酸接枝壳聚糖水凝胶的制备及其pH敏感性

利用迈克尔加成反应制备了两性聚电解质物质-丙烯酸接枝壳聚糖(ACS),利用FTIR和1HNMR对ACS进行结构表征,制备了丙烯酸接枝壳聚糖水凝胶(ACSG),并研究其pH敏感性和溶胀行为.结果如下:通过迈克尔加成反应,在壳聚糖分子链上引入了羧乙基基团;ACSG在pH值1.2～9.0溶液中均有较强的pH敏感性,酸敏,性优于碱敏性;ACSG在不同pH值溶液中的溶胀行为各不相同,在偏酸和偏碱性时溶胀度较大,pH值5.0时溶胀度最小;随着交联荆用量的增加,ACSG的溶胀度逐渐降低;随着取代度的增大,ACSG的溶胀度则先增大后减小.     

Application of syndiotacticity‐rich PVA hydrogels prepared at a low temperature to thermo‐ and pH‐responsive release devices

Three kinds of physically cross‐linked syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA) hydrogels were prepared at 0°C with use of the buffer solutions (BS) of pHs 4.0, 7.4, and 9.0. Three gels swelled at first and then began to shrink after 12 h when they were dipped in the same BS for preparation at higher temperature than 0°C. The release of Brilliant Blue (3 mg/1 mL) from the cylindrical gels prepared using BS of pH 7.4 was studied at 27, 37, and 47°C. Brilliant Blue has been released spending 4–12 h almost completely. The rate of release from the gel at temperatures of 27, 37, and 47°C became large with increasing temperature. The main factor on release of Brilliant Blue is not the contraction of gel, but swelling, because the degree of swelling (DS) became large with increasing temperatures for 27, 37, and 47°C. The rate of release from the gel (pH 4.0) was larger than that (pH 7.4) due to the increased DS of the hydrogel in early step at pH of 4.0. The apparent diffusion exponents of these releases at pH 7.4 evaluated from first 60% of the fractional release were lower than 0.45 due to the swelling during release. The exponent at pH 4.0 was 0.45 due to immediate swelling. The on‐off of shrinking behavior of atactic PVA (a‐PVA) hydrogel was observed under several temperature changes. The rate of release of Brilliant Blue at 5°C was lower than that at 27°C and no change was observed at 5°C after one on‐off cycle. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 41–46, 2000     

Synthesis,properties and self‐assembly of intelligent core‐shell nanoparticles based on chitosan with different molecular weight and N‐isopropylacrylamide

In this study, a series of chitosan‐graft‐poly(N‐isopropylacrylamide) (CTS‐g‐PNIPAAm) copolymers based on different molecular weight (Mw) of CTS and NIPAAm were synthesized through the polymerization of NIPAAm in an acid aqueous solution. The structures were verified by Fourier transform infrared and nuclear magnetic resonance. The influence of the CTS Mw on the properties of the resulting copolymers and self‐assembled nanoparticles was fully examined. The grafting ratio and grafting efficiency of the copolymers increased with the CTS Mw. All the copolymers have a similar low critical solution temperature of 33.5°C, which was independent of the CTS Mw. Furthermore, the copolymers were less temperature sensitive, when CTS Mw increased to 200 kDa. Besides, once the CTS Mw increased to 700 kDa, the copolymers were less pH sensitive near the tumor site (from pH 7.4 to 6.8). The copolymers could form uniform nanoparticles once the temperature increased to 34°C, which was reversible. After crosslinking by N,N‐methylenebisacrylamide (MBA), structurally stable nanoparticles could be obtained. The results from Transmission electron microscope (TEM) and Atomic force microscopy (AFM) showed that the MBA crosslinked nanoparticles were uniformly spherical with a loose structure. Surface tension method indicated that the critical aggregate concentrations were 0.045, 0.042, 0.037, and 0.036 mg mL^?1 prepared from CTS 50, 100, 200, and 700 kDa, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

HPMC/PNIPAAm温度敏感性水凝胶的制备及其对5-氟尿嘧啶的控制释放

以线型的羟丙基甲基纤维素(HPMC)和N-异丙基丙烯酰胺 (NIPAAm) 为原料,制备具有温度敏感性的半互穿网络水凝胶.采用荧光显微镜、红外光谱等对凝胶结构进行表征,并对不同HPMC / NIPAAm配比(W/W)的水凝胶的温度敏感性、溶胀和退溶胀动力学进行了研究.另外,以5-氟尿嘧啶(5-FU)为目标化合物,研究了...     

具有pH及温度敏感性的共聚物Poly(NIPAm-co-IA)水凝胶的合成及其性能研究

用自由基聚合合成了具有两水亲性的异丙基丙烯酰胺与衣康酸共聚物 ,对它们水溶液及其水凝胶的 p H及温敏性进行了研究。结果表明 ,在一定的范围内 ,随衣康酸含量增加、水溶液浓度减少和 p H值增大 ,共聚物水溶液的低临界溶解温度随之升高。共聚物水凝胶的溶胀率随温度升高呈下降趋势 ,并且 p H值低时的溶胀率随温度的升高而下降的趋势比 p H高时的要快 ,而且表现出明显的溶胀 -退胀可逆过程。     

DMFCs用磺化聚醚醚酮/磺化酚酞型聚醚砜共混质子交换膜

A sulfonated poly(ether ether ketone) (SPEEK) membrane with fairly high degree of sulfonation (DS) swells excessively and even dissolves at high temperature. To solve these problems, sulfonated phenolphthalein poly(ether sulfone) (SPES-C, DS 53.7%) is blended with the SPEEK matrix (DS 55.1%, 61.7%) to prepare SPEEK/SPES-C blend membrane. The decrease in swelling degree and methanol permeability of the membrane is dose-dependent. Pure SPEEK (DS 61.7%) membrane dissolves completely in water at 70ºC, whereas the swelling degree of the SPEEK (DS 61.7%)/SPES-C (40%, by mass) membrane is 29.7% at 80ºC. From room temperature to 80ºC, the methanol permeability of all SPEEK (DS 55.1%)/SPES-C blend membranes is about one order of magnitude lower than that of Nafion®115. At higher temperature, the addition of SPES-C polymer increases the dimensional stability and greater proton conductivity can be achieved. The SPEEK (DS 55.1%)/SPES-C (40%, by mass) membrane can withstand temperatures up to 150ºC. The proton conductivity of SPEEK (DS 55.1%)/SPES-C (30%, by mass) membrane approaches 0.16 S•cm－1, matching that of Nafion115 at 140ºC and 100% RH, while pure SPEEK (DS 55.1%) membrane dissolves at 90ºC. The SPEEK/SPES-C blend membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.     

Swelling Kinetics of HPMC Tablets

Hydroxypropyl methylcellulose (HPMC) is a cellulosic polymer widely employed in tablets formulation. In contact with biological fluids, it undergoes a glassy–rubbery transition and drug release is strongly influenced by swelling. We study the kinetic parameters of a classical phenomenological model (Astarita and Sarti), which describes the velocity of a glassy–rubbery interface as a function of the local solvent concentration. One-dimensional mass transport equations with moving boundaries are numerically solved by finite elements method in order to fit Astarita–Sarti parameters k and n on experimental swelling fronts and concentration profiles taken from literature for HPMC K4M, HPMC K15M, and HPMC K100M.     

The influence of pH,hydrolysis and degree of substitution on the temperature‐sensitive properties of polyaspartamides

Temperature‐sensitive polyaspartamide obtained by the aminolysis reaction of polysuccinimide with isopropylamine has been proposed as a good material for biomedical applications. The polymer is susceptible to hydrolysis producing carboxyl groups; thus the temperature‐sensitive behavior of the polymer depends on pH. A set of polyaspartamides was synthesized with different degrees of hydrolysis (DH) and substitution (DS). The influence of DH, DS and pH on the lower critical solution temperature (LCST) of the polyaspartamides was studied. The LCST of the polyaspartamides increases as the pH increases and at the same pH the polymer with higher DH presents a higher LCST. Also, at the same pH an increment in the DS produces a decrease in the LCST. These tendencies are explained by the presence of a carboxylate group on the polyaspartamide structure. The behaviors can be tailored as functions of DS and DH enabling the use of temperature‐sensitive polyaspartamide in different biomedical applications where pH and/or temperature changes will trigger a drug delivery. © 2018 Society of Chemical Industry     

HPMC layered tablets modified with chitosan and xanthan as matrices for controlled‐release fertilizers

Polymeric matrices based on hydroxypropyl methylcellulose (HPMC) with xanthan (X) or chitosan (Q) and using KNO₃ as a model fertilizer were prepared as three‐layered tablets and assayed as controlled release fertilizers (CRFs). The dynamic swelling behavior was analyzed in order to interpret the water uptake mechanism, which in general proved to be non‐Fickian. The presence of HPMC allows a substantially constant rate of fertilizer release. The release mechanism of KNO₃ was analyzed and can be described as non‐Fickian diffusion, with release exponents ranging from 0.85 to 1.01, suggesting polymer relaxation as the major process controlling fertilizer release. Durability in soil indicates the blend Q‐HPMC as the more long‐lasting matrix of those tested, remaining at least 34 weeks. Both blends improve HPMC properties for agronomical applications, with X‐HPMC increasing the swelling rate and Q‐HPMC extending the permanence in the soil. Therefore, layered X‐HPMC and Q‐HPMC matrices can be proposed as suitable materials for the development of CRFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40839.     

Preparation,Characterization, and Drug-Release Behaviors of a pH-Sensitive Composite Hydrogel Bead Based on Guar Gum,Attapulgite, and Sodium Alginate

A novel guar gum-g-poly (acrylic acid)/attapulgite/sodium alginate (GG-g-PAA/APT/SA) composite hydrogel bead with excellent pH sensitivity was prepared via a facile ionic gelation approach and characterized by FTIR and SEM techniques. The effect of APT content on the encapsulation efficiency (EE), swelling ratio, and drug release behaviors of the beads was investigated and the in-vitro release kinetics were also evaluated using diclofenac sodium (DS) as the model drug. The results indicate that the burst release effect of DS drug was eliminated due to the incorporation of APT, and the DS cumulative release was clearly decreased with increasing the APT content.