热逆变水凝胶及其固定化酶的特性

由Ｎ－异丙基丙烯酰胺及其共聚物合成的水凝胶，当温度升高或降低时，会发生相应的体积收缩或膨胀变化。将酶固定在这种水凝胶中，随着温度的循环变化，它能可逆地开启或关闭酶的活性。本文对热逆变水凝胶固定化天冬酰胺酶的活性随温度的变化进行了研究，发现酶的活性随温度的变化而发生有规律的变化。     

混合酸制备壳聚糖温敏水凝胶的研究

提出了以醋酸-盐酸混合液为溶剂,制备壳聚糖-αβ甘油磷酸钠水凝胶。探讨了它们对壳聚糖水凝胶性能的影响,并从分子间相互作用力的角度对各种现象进行了理论解释。实验结果表明:采用混合酸为溶剂,能够简单地对凝胶的粘度和凝胶化时间进行控制,并且pH对这种体系影响较小。     

壳聚糖/聚醚半互穿网络水凝胶的性能

以壳聚糖和聚醚为原料,戊二醛为交联剂,在醋酸溶液中制备了壳聚糖/聚醚水凝胶,反应温度45℃,聚醚和壳聚糖的质量比为0.4,戊二醛浓度为0.053 mol/L,壳聚糖黏均相对分子质量为24.86×104时,其凝胶饱和溶胀度为876.25%;反应温度45℃,聚醚和壳聚糖的质量比为0.6,戊二醛浓度为0.267 mol/L,壳聚糖黏均相对分子质量为24.86×104时,其凝胶硬度为151.896 kPa。     

聚乙烯吡咯烷酮半互穿网络智能凝胶的合成和电场行为研究

利用化学交联法,制备了由聚乙烯吡咯烷酮(PVP)和丙烯酰胺(Am)、丙烯酸(AA)复合的具有半互穿网络(Semi-IPNs)结构的高分子水凝胶。研究了凝胶在直流电场作用下NaCl溶液中的溶胀、弯曲行为及交联剂含量、PVP含量对水凝胶的溶胀性质、拉伸强度的影响。结果表明凝胶的最大弯曲率随着时间和电场强度的增加而增大,随溶液离子浓度的增加呈现出最大值。增加PVP可以提高拉伸强度降低弯曲度,适当增加交联剂,可以加强拉伸强度108.51%,降低溶胀度68.29%。     

PAAm／PEG／PVP半互穿网络水凝胶的制备、表征及茶碱释放研究．

以N,N-亚甲基双丙烯酰胺（N,N-MBA）为交联剂、过硫酸钾（KPS）为引发剂·通过丙烯酰胺（AAm）、聚乙二醇（PEG）和聚乙烯吡咯烷酮（PVP）发生共聚反应制备具有半互穿网络结构的水凝胶PAAm／PEG／PVP。采用红外光谱（FTIR）、热重分析（TG）对水凝胶的结构和热学性质进行了分析,研究了中性条件下水凝胶的溶胀性能,并进一步研究了其负栽茶碱在不同缓冲溶液中的释放行为。     

采用压敏凝胶和变压循环增强传质──改善固定化酶促反应的新途径

引言聚合物凝胶是最常用的酶固定化材料．然而凝胶固定而曲折的孔结构又具有较大的传质阻力．底物、产物、营养物等在固定化材料中受到的阻滞使催化反应减慢，从而成为固定化酶促反应中最严重的问题．环境敏感性凝胶为克服固定化酶中的高传质阻力提供了新思路．这种凝胶可随pH值、温度、溶剂组成或电场等的微小变化而产生体积的显著改变，并已在生化分离，化学驱动器、药物控制释放及人工肌肉等领域显示了良好的实用前景．Hoffman等的研究又显示了温敏性凝胶在固定化酶和细胞上的潜在应用价值。以此为基础，并基于Lee等关于凝胶压敏性的新…     

pH敏感瓜胶/聚丙烯酸半互穿网络水凝胶研究

制备了瓜胶/聚丙烯酸(GG/PAA)的半互穿网络(sem i-IPN)水凝胶,以N,N-亚甲基双丙烯酰胺(MBA)为交联剂,考察了加料量、溶胀介质pH对平衡溶胀率(ESR)的影响。结果表明:GG/PAA半互穿网络水凝胶的ESR在pH≤3时较小,pH>4后增加较快,pH=8.2时达最大值,继续增加pH,ESR又呈下降趋势,体系具有pH敏感性。在pH相同条件下,ESR随GG用量增加而减小,随丙烯酸(AA)用量增加而增大。pH=8.2、ρ(GG)从5 g/L增加到25 g/L时,ESR从3 142降低到1 026;当ρ(AA)用量从125 g/L增加到375 g/L时,ESR从1 195增加到2 611。m(MBA)∶m(AA)=(0.5∶100)~(1.2∶100)时,ESR略有增加。GG/PAA半互穿网络水凝胶的溶胀动力学表明,该类凝胶满足在胃液pH环境中溶胀率较小、小肠部位pH环境中溶胀率较高的要求,因此,通过调整配方,结合瓜胶只被结肠部位细菌降解的特性,GG/PAA半互穿网络水凝胶有望成为一种理想的靶向结肠给药载体。     

温度及pH敏感性互穿网络水凝胶的制备研究

采用分步法制备了聚丙烯酸/N-异丙基丙烯酰胺互穿网络水凝胶,研究了互穿网络水凝胶的溶胀性能。结果表明,当水溶液的pH增大时,水凝胶的溶胀率显著增加。在一定的温度范围内,水凝胶的溶胀率随温度升高而减小。聚丙烯酸/N-异丙基丙烯酰胺互穿网络水凝胶表现出显著的温度及pH敏感双重特性。     

溶胶-凝胶包埋固定化酶的研究

介绍了溶胶-凝胶(sol-gel)包埋法制备固定化酶的基本过程和影响因素,着重论述了S iO2、有机改性硅胶和有机/无机杂化硅胶三类溶胶-凝胶基质材料制备固定化酶的特性和在催化反应中的应用,对溶胶-凝胶包埋法制备高性能固定化酶的发展前景予以展望。     

Synthesis of fluorescent ABA triblock copolymer via click reaction

A hyperbranched–linear–hyperbranched (ABA) triblock copolymer containing poly(ethylene glycol) (PEG) as linear block and polyglycerol (hbPG) as hyperbranched blocks has been synthesized through a copper‐catalysed click reaction. In order to synthesize the hyperbranched block, propargyl alcohol‐initiated ring‐opening multibranching polymerization of glycidol was used to prepare hbPG with the propargyl segment in the focal point (CH?C? hbPG). Separately, PEG was functionalized at both ends using cyanuric chloride, and then the chloride groups of cyanuric chloride were substituted by azide groups. Finally, the azide‐functionalized PEG was conjugated to CH?C? hbPG via a click reaction. Substitution of the chlorine atoms of cyanuric chloride under different conditions together with click chemistry allows the synthesis of a variety of polymeric architectures. In the last step, fluorescein was attached to the block copolymer as a fluorescent probe in order to study the cell internalization of this copolymer. This type of triblock copolymer is a promising future nanomaterial for simultaneous drug delivery and cell imaging. © 2016 Society of Chemical Industry     

Hyperbranched polyesters based on hydroxyalkyl‐lactones via thiol‐ene click reaction

The preparation of AB₂ monomers via thiol‐ene click reaction from six‐ and seven‐membered unsaturated lactones is described. The hydroxyl‐functionalized valerolactone was prepared by use of Michael thiol‐ene‐addition reaction starting from 2‐mercaptoethanol and 3‐methylenetetrahydro‐2H‐pyran‐2‐on. The hydroxyl‐functionalized caprolactone was prepared radically from 2‐mercaptoethanol and 7‐allyloxepan‐2‐one. Both AB₂ monomers were polymerized via ring opening in the presence of tin(II)‐2‐ethylhexanoate (Sn(Oct)₂) as a catalyst yielding the hyperbranched polyesters. The new hyperbranched polyesters were analyzed by ¹³C NMR spectra to determine the degree of branching. © 2014 Society of Chemical Industry     

基于点击反应的单宁衍生物的合成及其性能

植物单宁与溴丙炔反应制备的炔化单宁与对十二烷基苯磺酰叠氮通过点击反应合成单宁衍生物。采用红外光谱仪和元素分析仪对单宁衍生物的结构进行表征,并研究其表面张力、抗氧化能力以及对细菌的抑制作用等性能。结果表明,在单宁分子的结构中引入长链烷基后,改善其亲脂性,制备出的单宁衍生物能显著降低水溶液的表面张力,当单宁衍生物质量浓度为0.8mg/mL时,可降低水溶液的表面张力至28.94mN/m;单宁衍生物对1,1-二苯基-2-苦基苯肼基自由基具有较强的清除能力,当单宁衍生物质量浓度为0.25mg/mL时,对1,1-二苯基-2-苦基苯肼基自由基的最大清除率可达97.08%;由于单宁脂溶性的增加及具有抗菌性能的三氮唑基团的引入,单宁衍生物对大肠杆菌和金黄色葡萄球菌的抑制作用明显增强。     

Synthesis and characterization of hyperbranched polytriazole via an ‘A2 + B3’ approach based on click chemistry

BACKGROUND: The ‘A₂ + B₃’ type of polymerization has been demonstrated to be an alternative route towards hyperbranched polymers. Some highly crosslinked hyperbranched polymers have been prepared via copper(I)‐catalyzed click reactions of multivalent azides and alkynes. To obtain hyperbranched polymers without gelation and develop the A₂ + B₃ type of polymerization based on click reactions, the specific reaction conditions need to be investigated. RESULTS: In this work, a hyperbranched polytriazole (hb‐PTA) was synthesized through the A₂ + B₃ approach using a click reaction. 4‐N,N′‐bis(2‐azidoethyl)amino‐4′‐nitroazobenzene and 1,3,5‐tris(alynyloxy)benzene were synthesized for use as the A₂ and B₃ monomers, respectively. This was a ‘one‐pot’ polymerization carried out using a slow‐addition method. The obtained hb‐PTA was soluble in common organic solvents. The molecular structure was characterized using ¹H NMR, Fourier transform infrared and gel permeation chromatography analyses. The degree of branching of hb‐PTA was determined to be around 0.50. CONCLUSION: The hb‐PTA was successfully synthesized via the A₂ + B₃ approach based on a click reaction. The polymerization conducted in dilute solution adopting slow addition of A₂ to B₃ resulted in hb‐PTA in the absence of gelation. The obtained hb‐PTA exhibited high thermal stability. Copyright © 2008 Society of Chemical Industry     

Synthesis and photoinitiating activity study of polymeric photoinitiators bearing BP moiety based on hyperbranched poly(ester‐amine) via thiol‐ene click reaction

A series of polymeric photoinitiators (BP‐HPEAs) bearing BP moiety based on hyperbranched poly(ester‐amine) were synthesized via the thiol‐ene click reaction of 3‐(4‐benzoylphenoxy)propyl 2‐mercaptoacetate (BPPM) with acrylated HPEA. BPPM was obtained by the esterification of (4‐(3‐hydroxypropoxy) phenyl) phenyl methanone (HPPM) with mercaptoacetic acid in the presence of p‐toluene sulphonic acid as a catalyst. HPEA was prepared through Michael addition of piperazine with tri(hydroxymethyl)propane triacrylate. Their molecular structures were confirmed by the ¹H NMR, ¹³C NMR, and FTIR analysis. The UV–vis spectrum analysis results showed that BP‐HPEAs exhibit the stronger n–π* absorption at ～ 340 nm with over two times higher molar extinction coefficients than BP at the concentration of 1.00 × 10^?3M. The photoinitiating activity study showed that the maximum photopolymerization rates of 1,6‐hexanediol diacrylate initiated by BP‐HPEAs in the absence of coinitiator were obtained by two times higher than that by BP in the presence of triethylamine as a coinitiator. Moreover, the excellent miscibility of BP‐HPEAs with the commercial bisphenol A epoxy diacrylate was achieved according to the T_s/T_g ratios of over 9.0 from DMTA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Surface modification of calcium carbonate by thiol-ene click reaction and its effect on the performance of PVC composite

Disposable PVC gloves are cost effective, but their mechanical properties can be compromised at extremely high concentrations of plasticizers. The tensile properties of PVC gloves can be improved by incorporating modified fillers into the PVC matrix. In this research, calcium carbonate (CaCO₃) was functionalized with γ-methacryloxy propyl trimethoxyl silane (KH-570) and then further modified through a click reaction with n-Octadecyl mercaptan. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy have confirmed that n-Octadecyl mercaptan-modified KH-570 was successfully grafted onto the surface of CaCO₃. Composite films were manufactured by blending either pristine CaCO₃ or modified CaCO₃ with PVC resin paste and their tensile properties, light transmission, moisture permeability, and solvent resistance were evaluated. Compared with CaCO₃/PVC and KH-570-modified CaCO₃/PVC composite films, n-Octadecyl mercaptan-modified CaCO₃/PVC composite films showed higher light transmittance, lower moisture permeability, and higher tensile properties. Dynamic mechanical analysis revealed that these films had low glass transition temperatures, thus broadening their applicability to low-temperature conditions.     

Temperature and pH responsive hydrogels based on polyethylene glycol analogues and poly(methacrylic acid) via click chemistry

A novel temperature responsive copolymer, poly[2‐(2‐methoxyethoxy)ethyl methacrylate‐co‐oligo(ethylene glycol)methacrylate‐co‐N‐hydroxymethyl acrylamide] [P(MEO₂MA‐co‐OEGMA‐co‐HMAM)], was synthesized by atom transfer radical polymerization. pH responsive poly(methacrylic acid) (PMAA) was synthesized by reversible addition‐fragmentation chain transfer polymerization. After the hydroxyl groups on P(MEO₂MA‐co‐OEGMA‐co‐HMAM) were transformed into azide groups and the carboxyl groups on PMAA were transformed into alkyne groups respectively, a novel temperature and pH responsive hydrogel was fabricated by click chemistry between the azide‐P(MEO₂MA‐co‐OEGMA‐co‐HMAM) and alkyne‐PMAA in the presence of CuSO₄ and sodium ascorbate in aqueous solution. The rheological kinetics of gel formation demonstrated that gelation had commenced within 5 min at 25 °C, since then the storage modulus (G′) was higher than the loss modulus (G″). SEM images of hydrogel morphology and the swelling ratios of hydrogel at different temperatures and pH proved that the formed hydrogel had temperature and pH sensitivities. Bovine serum albumin was used as a model to evaluate the sustained release of the hydrogel; the results indicated that the hydrogel was a promising candidate for controlling protein drug delivery. © 2015 Society of Chemical Industry     

Fabrication of polymer‐dispersed liquid crystals with low driving voltage based on the thiol‐ene click reaction

Polymer‐dispersed liquid crystals (PDLCs ) with a well‐defined polymer matrix were successfully fabricated by the thiol‐ene click reaction based on poly(ethylene glycol) diacrylate (PEGDA ) and trimethylolpropanetris‐(3‐mercaptopropionate) (TMTP ). UV ?visible spectrophotometry, Fourier transform IR spectroscopy, SEM and polarized optical microscopy were employed to explore the PDLC films obtained. Electro‐optical properties were studied with a UV ?visible spectrophotometer. It was found that the PDLC films with optimal thiol content fabricated by the thiol‐ene click reaction showed high transmittance, low driving voltage and a low memory effect. It was concluded that the driving voltage change of PDLCs with different thiol concentrations was caused by the polymerization rate and the structure of the polymer matrix. © 2017 Society of Chemical Industry     

Star graft copolymer via grafting‐onto strategy using a comb!ination of reversible addition–fragmentation chain transfer arm‐first technique and aldehyde–aminooxy click reaction

A facile synthetic pathway to a multi‐arm star graft polymer has been developed via a grafting‐onto strategy using a combination of a reversible addition–fragmentation chain transfer (RAFT) arm‐first technique and aldehyde–aminooxy click reaction. A star backbone bearing aldehyde groups was prepared by the RAFT copolymerization of acrolein (Ac), an existing commercial aldehyde‐bearing monomer, with styrene (St), followed by crosslinking of the resultant poly(St‐co‐Ac) macro‐RAFT agent using divinylbenzene. The aldehyde groups on the star backbone were then used as clickable sites to attach poly(ethylene glycol) (PEG) side chains via the click reaction between the aldehyde groups and aminooxy‐terminated PEG, leading to a structurally well‐defined star graft copolymer with arms consisting of poly(St‐co‐Ac) as backbone and PEG as side chains. Crystalline morphology and self‐assembly in water of the obtained star graft copolymer were also investigated. Opportunities are open for the star graft copolymer to form either multimolecular micelles or unimolecular micelles via control of the number of grafted PEG side chains. © 2013 Society of Chemical Industry