快速响应聚(N-异丙基丙烯酰胺)水凝胶的制备及性能

以N-异丙基丙烯酰胺为单体、N,N′-亚甲基双丙烯酰胺为交联剂、过硫酸铵为引发剂、N,N,N,′N′-四甲基乙二胺为加速剂,在不同浓度的羧甲基纤维素的水溶液中,在低温下聚合/交联制备了一系列快速响应的温度敏感性聚(N-异丙基丙烯酰胺)水凝胶。用SEM观察了其表面形态,测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。结果表明,与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且对温度的变化具有较快的响应速率。以质量分数为0.75%的羧甲基纤维素水溶液中制备的水凝胶为例,该水凝胶在20℃时的溶胀比为21.4,而传统水凝胶在相同温度时的溶胀比仅为12.9;该水凝胶在1 m in内失去60%的水,在4 m in内失去约80%的水,而传统水凝胶在15 m in内仅失去66%左右的水。     

尼龙11/蒙脱土纳米复合材料形态和性能研究

通过熔融共混法成功地制备了不同含量蒙脱土的尼龙11/蒙脱土纳米复合材料,利用X衍射(XRD)和透射电镜(TEM)研究了尼龙11/蒙脱土纳米复合材料的微观结构。结果表明,当蒙脱土质量分数小于2%时,形成了剥离型的纳米复合材料,当蒙脱土质量分数超过2%时形成了插层型的纳米复合材料。热重分析表明当蒙脱土质量分数为2%时,纳米复合材料的热分解温度比纯尼龙11提高了27℃。不同蒙脱土含量的纳米复合材料悬臂梁冲击强度均比纯尼龙11的高,但其拉伸强度在蒙脱土质量分数小于8%时降低,以后随蒙脱土含量的增加而提高。     

尼龙6-聚乙烯合金/蒙脱土纳米复合材料的制备与物理机械性能

用熔融插层法制备了尼龙6-聚乙烯合金/蒙脱土纳米复合材料.X射线衍射表明,在有机蒙脱土质量分数为4%,6%时,蒙脱土被剥离成片层分散在基体中;进一步提高蒙脱土质量分数至10%,蒙脱土部分剥离,部分插层.物理机械性能测试结果表明,将有机蒙脱土加入尼龙6-聚乙烯合金中能显著提高复合材料的拉伸强度、弯曲强度、冲击强度.其中冲击强度最大可以提高100%以上.     

蒙脱土和硼酸镧复合纳米润滑油添加剂的摩擦学性能研究

将KH550偶联剂修饰的纳米蒙脱土和KH550偶联剂修饰的纳米硼酸镧,按不同质量分数的纳米蒙脱土与相同质量分数的纳米硼酸镧复合物和单一不同质量分数的纳米蒙脱土分别加入到150N基础油中,制备质量分数0%～4%的5种纳米蒙脱土与纳米硼酸镧复合添加剂的润滑油和质量分数0%～4%的5种单一纳米蒙脱土添加剂润滑油体系,在四球摩擦实验机上考察了纳米蒙脱土和纳米硼酸镧复合润滑油添加剂的摩擦学性能。实验结果表明:当其添加2%的纳米蒙脱土和2%的纳米硼酸镧的复合物具有良好的抗磨减磨性能。     

聚氨酯/蒙脱土纳米复合材料的制备及其性能研究

采用原位聚合方法制备了聚氨酯/蒙脱土纳米复合材料,并对其性能进行了测试,结果表明,TDI的功能基团-NCO与蒙脱土发生接枝反应,当OMT质量分数为2%时,纳米复合材料的综合力学性能达到最佳,耐溶胀性能得到明显的改善,耐热性能有所提高。     

原位接枝插层法制备聚丙烯/蒙脱土纳米复合材料

采用原位接枝插层法制备了聚丙烯/蒙脱土纳米复合材料.借助长链有机胺有机化的蒙脱土在溶液中与马来酸酐和少量辅助溶胀剂进行溶胀;溶胀后的有机蒙脱土再与聚丙烯、适量引发剂在Haake混炼机中进行熔融反应,得到一种聚丙烯/蒙脱土接枝插层共混物;再将接枝插层共混物按一定比例与聚丙烯在Haake混炼机中进行混炼得到聚丙烯/蒙脱土纳米复合材料.用X射线衍射仪(XRD)、透射电镜(TEM)和热失重分析仪(TGA)分别对各步骤的产物进行表征.产物的XRD和TEM分析结果表明蒙脱土完全剥离并均匀分散在聚丙烯基体中,形成了真正的聚丙烯/蒙脱土纳米复合材料.TGA分析结果显示出该纳米复合材料具有相当好的热稳定性.     

剥离型酚醛树脂/蒙脱土纳米复合材料研究

用十六烷基三甲基溴化铵(CTAB)对蒙脱土进行了有机化处理,使蒙脱土由亲水性变成亲油性。采用XRD、FTIR及TEM研究了有机蒙脱土及其在酚醛树脂中的剥离行为,制备了酚醛树脂/蒙脱土纳米复合材料并测试了其层间剪切性能和烧蚀性能。实验结果表明,经CTAB处理的蒙脱土与酚醛树脂具有良好的相容性,且CTAB的含量较多时所制得的有机蒙脱土的结构较好,根据Bragg方程计算,CTAB用量超过蒙脱土量50%时,蒙脱土的片层间距由原来的1.48 nm增加到2.33 nm;有机蒙脱土用量小于5%时生成完全剥离型酚醛树脂/蒙脱土纳米复合材料;与碳布增强酚醛树脂复合材料相比,碳布增强酚醛树脂/蒙脱土纳米复合材料的力学性能和烧蚀性能均有一定的提高和改善,层间剪切强度随蒙脱土含量的增多而增大,蒙脱土用量为15%时,层间剪切强度提高了27.1%,线烧蚀率在用量为3%时降低了48.5%,质量烧蚀率变化不明显。     

聚氨酯/有机蒙脱土纳米复合材料的合成与表征

采用共沸法精制有机蒙脱土，估算了有机蒙脱土中吸附水质量分数约为8．3％。结构水的质量分数约为4．1％。用两步法原位聚合制备了聚氨酯／有机蒙脱土(PU／MMT)纳米复合材料，表征了纳米复合材料的形态、动态力学性能和物理机械性能。结果表明，有机蒙脱土对聚氨酯有增强和增韧双重作用。有机蒙脱土对聚合物分子的限制作用使PU／MMT纳米复合材料的玻璃化转变温度升高，储能模量和损耗模量也有明显提高。     

醛酸共聚物/蒙脱土纳米复合材料的制备及性能研究

用水溶性聚合单体甲基丙烯酸和丙烯醛在钠基蒙脱土层间直接原位插层聚合,制备了水溶性醛酸共聚物/蒙脱土纳米复合材料。考察了引发剂用量及蒙脱土用量对纳米复合材料结构及应用性能的影响,并用X射线衍射和傅立叶变换红外光谱对纳米复合材料的结构进行了表征。研究结果表明:用坯革质量6%的纳米复合材料结合质量分数2%铬粉鞣制,可使坯革的收缩温度达90℃以上,增厚率达到70%以上,与常规铬鞣相比,可减少75%的铬粉用量。FTIR和XRD结果表明,所制备的纳米复合材料属于剥离型纳米复合材料,甲基丙烯酸与丙烯醛在蒙脱土层间发生了原位聚合。     

有机蒙脱土／硅橡胶膜的制备及吸水性能研究

采用不同碳链长度的季铵盐作为插层剂改性钠蒙脱土,以硅橡胶为基体,用溶液插层法制备有机蒙脱土／硅橡胶纳米复合材料。系统分析了有机蒙脱土对硅橡胶吸水性能的影响,包括胶膜吸水性和吸水后的力学性能。通过X射线、红外表征了有机蒙脱土的结构。实验结果袁明,烷基碳原予数越多,所制备的有机蒙脱土／硅橡胶纳米复合材料对水的阻隔性越好;当蒙脱土质量分数为3％时,吸水性最低,吸水后力学性能下降幅度最小。     

Nanocomposite Hydrogels with High Mechanical Strength and High Swelling Ratio by RAFT Polymerization

Nanocomposite hydrogels (NC gels) have been prepared based on poly(N-isopropylacrylamide) (PNIPAM) containing 0.25-15 wt% of the expandable synthetic hectorite Laponite XLS (Clay-S) by reversible addition fragmentation chain transfer (RAFT) polymerization. The swelling behaviors were investigated and the hydrogels by RAFT polymerization (RAFT gels) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional hydrogels (CGel). This could be attributed to the presence of dangling chains mainly caused by chain transfer reagent (CTA), which could retard the crosslinking reaction rate greatly. Furthermore, the NC gels have stronger mechanical strength than CGel. The presence of Clay-S does not affect the value of the lower critical solution temperature (LCST).     

Poly(N-isopropylacrylamide) hydrogels with improved shrinking kinetics by RAFT polymerization

Functional poly(N-isopropylacrylamide) (PNIPAM) hydrogels were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) in the presence of N,N-methylenebisacylamide (BIS) as a cross-linker and 4-cyanopentanoic acid dithiobenzoate as chain transfer reagent (CTA). The swelling behaviors were investigated and the hydrogels by RAFT polymerization (RAFT gels) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional hydrogel (CG). It could be attributed to the presence of dangling chains mainly caused by CTA, which could retard the crosslinking reaction rate greatly. Another CTA, 3-(trithiocarbonyl) propanoic acid, was adopted to further investigate the effect of CTA. It showed the similar effect except the different accelerated degree to the shrinking kinetics. Furthermore, the living character of the RAFT process was used to polymerize a new batch of monomer (NIPAM) from functional RAFT gels to introduce grafted structure. The PNIPAM-g-PNIPAM hydrogels indicted further accelerated shrinking kinetics than functional backbone hydrogels.     

温度和pH双重敏感性水凝胶的制备及表征

在5种不同温度下聚合交联,制备了一系列温度和pH双重敏感性聚(N-异丙基丙烯酰胺-co-衣康酸)水凝胶。实验发现,15、25℃得到的凝胶是透明的,45、55℃得到的凝胶是白色不透明的,而在相转变温度附近(35℃)得到的凝胶则是半透明的。FTIR测定表明,它们具有相似的化学组成和结构。SEM观察证实,它们具有不同的表面形态。测定了不同温度和pH下达到平衡时水凝胶的溶胀比,考察了水凝胶在水和强酸性溶液中的去溶胀动力学。结果表明,与15℃或25℃制备的水凝胶相比,45℃和55℃制备的水凝胶的性能有显著提高:(1)溶胀比大为增加。15℃或25℃制备的水凝胶在25℃时溶胀比分别为65.3和68.1,而45℃和55℃制备的水凝胶此时溶胀比分别高达105.7和110.1;(2)45℃和55℃制备的水凝胶在极端环境下对温度的变化仍具有较快的响应速率。例如在温度为60℃,pH=1.67的强酸条件下,45℃和55℃制备的水凝胶在60 min内皆可失去95%的水,而15℃或25℃制备的水凝胶在120 min内只能失去42%左右的水。     

Preparation and Controlled Drug Release Characteristics of Thermoresponsive PEG/Poly (NIPAM-co-AMPS) Hydrogels

Thermosensitive hydrogels were prepared by free radical polymerization of N-isopropylacrylamide (NIPAM) and 2-acrylamido-2-methylpropanesulphonic acid (AMPS) in presence of polyethylene glycol (PEG) as macroinitiator. The incorporation of functional monomer in the hydrogel was confirmed by infrared spectroscopy. The equilibrium swelling ratio (ESR), deswelling rate, volume transition temperature, and surface morphology of synthesized hydrogels are found to be dependent on concentration of AMPS monomer in the feed composition. The equilibrium swelling ratio (ESR) and water retention properties increase with increasing AMPS concentration in hydrogels and decrease with increasing salt concentration in external medium. The hydrogel with high dose of AMPS has high loading efficiency of theophylline drug, whereas the in-vitro release of the drug is delayed for a prolonged period in swollen gels above LCST of PNIPAM.     

Controllable synthesis of a novel poly(vinyl alcohol)‐based hydrogel containing lactate and PEG moieties

Tunable hydrogel that contained well‐defined poly(vinyl alcohol) (PVA), labile lactate groups, and hydrophilic poly(ethylene glycol) (PEG) segments was prepared through a combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and esterification reaction. A diol was prepared via the esterification between lactic acid (LA) and PEG. Then the diol was allowed to react with maleic anhydride to produce a diacid. Meanwhile, well‐defined PVA was synthesized by the alcoholysis of poly(vinyl acetate) (PVAc) obtained by RAFT polymerization of vinyl acetate. The hydrogels with tailor‐made structure were generated by crosslinking PVA with LA‐based diacid. The structures and properties of LA‐based intermediates and the hydrogels were characterized with Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Both LA‐based diol and diacid were semicrystalline and water‐soluble, their melting temperature and glass transition temperature were 52 and ?51, 54 and ?41°C, respectively. The polydispersity indexes of the precursor of PVA samples were within the range of 1.03–1.10. It was found that the thermal stability of hydrogel was higher than that of LA‐based diacid. Both the swelling and release properties of the hydrogels depend on the feeding ratio of PVA/LEM and the chain length of PVA, which reflected that the structure and properties of the hydrogels were controllable. POLYM. ENG. SCI., 54:1366–1371, 2014. © 2013 Society of Plastics Engineers     

Water sorption behavior of CMC/PAM hydrogels prepared by γ-irradiation and release of potassium nitrate as agrochemical

Novel types of highly swelling CMC/PAM hydrogels have been prepared by grafting cross-linked polyacrylamide (PAM) chains onto carboxymethylcellulose (CMC) via a free radical polymerization method using γ-irradiation. The prepared CMC/PAM hydrogels were characterized by FT-IR spectral analysis. The AM content and irradiation dose had a direct effect on gel content of CMC/PAM hydrogels and inverse effect on their swelling ratio. The hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics which were highly dependent on the chemical composition of the hydrogel, pH and ionic strength of the medium in which the hydrogel was immersed. The results were supported by morphological properties of CMC/PAM hydrogels by using SEM. The kinetics of water uptake and the water transport mechanism were studied as a function of the CMC/AM ratio into the prepared hydrogel. The release rate of potassium nitrate entrapped within the CMC/PAM matrix increased by enhancing its loading %, and decreased with lowering AM content and irradiation dose.     

羟丙基纤维素RAFT聚合温敏性聚（N异丙基丙烯酰胺）水凝胶的合成及表征

用羟丙基纤维素(HPC)接枝的多链转移官能基大分子链转移剂,通过可逆加成断裂链转移(RAFT)聚合制备了羟丙基纤维素接枝聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶(HPC-g-PNIPAM hydrogel),研究了HPC相对分子质量、RAFT分子接枝密度以及HPC和NIPAM质量比对水凝胶微观形貌、低临界溶解温度(LCST)以及溶胀性能和机械性能的影响。结果表明,HPC大分子RAFT聚合PNIPAM能获得具有高溶胀比和快速响应性能的水凝胶;HPC的引入能提高水凝胶机械强度。RAFT聚合方法和少量大分子纤维素RAFT分子的引入会略微降低LCST,但当HPC组分增加到一定量,又会使LCST升高。     

Synthesis of rapid responsive gels comprising hydrophilic backbone and poly(N-isopropylacrylamide) graft chains by RAFT polymerization and end-linking processes

A thermosensitive poly(N-isopropylacrylamide) (PNIPAM) grafted gel, which comprises hydrophilic backbone and freely mobile PNIPAM graft chains, was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and end-linking processes. Functional PNIPAM bearing dithiobenzoate end group (-C(S)S-R) was prepared first, and then it was reacted with divinyl compounds to obtain gel. In order to adjust the composition of the gels, two divinyl compounds, N,N-methylenebisacrylamide (BIS) and poly(ethylene glycol) diacrylate (PEGDAC), were used. The cross-linking polymerization mechanism was proposed. The swelling and deswelling kinetics of the hydrogels were measured. The gels exhibit rapid deswelling kinetics. At the same time, they show rapid swelling kinetics within 30 min, whereas a conventional PNIPAM-co-PEG-co-BIS gel with the same feed composition requires more than 10 h to reach swelling equilibrium.     

A comparative study of swelling properties of hydrogels based on poly(acrylamide‐co‐methyl methacrylate) containing physical and chemical crosslinks

Poly (acrylamide‐co‐methyl methacrylate) hydrogels of different ratios were prepared by using chemical and physical crosslinks to study the effect of nature of crosslinks on swelling behavior of hydrogels. The chemically crosslinked gels were prepared by using NN′‐methylene bis acrylamide, while physically crosslinked hydrogels were prepared by precipitation polymerization method, using dioxane as solvent. Detailed swelling kinetics such as swelling ratio, transport exponent n, diffusion coefficient D and the effect of pH on equilibrium swelling studies. The study revealed that the nature of crosslinks alter the swelling characteristics of the hydrogel. In chemically crosslinked hydrogels the water transport is Fickian in nature, while in the case of the physically crosslinked hydrogels the water transport mechanism is anomalous indicating major change in relaxation mechanism due to nature of crosslinks. The results also indicate that with increasing acrylamide content the swelling ratio of the hydrogels were also increased, but the transport exponent n remains nearly constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 779–786, 2003