温度和pH敏感性壳聚糖接枝物对辅酶A的控制释放

利用接枝共聚合成了具有聚丙烯酸(PAA)和聚异丙基丙烯酰胺(PNIPAm)支链的壳聚糖(CS)聚合物〔P(CS-g-AA/PNIPAm)〕,研究了其水溶液的温度和pH敏感性,并利用其性能探讨了P(CS-g-AA/PNIPAm)对辅酶A的控制释放。紫外光谱分析结果表明,P(CS-g-AA/PNIPAm)水溶液比异丙基丙烯酰胺均聚物的最低临界溶解温度(LCST)略高。在pH=9、温度为24~50℃或温度为24℃、pH=3.7~9的条件下,聚合物都能对辅酶A(CoA)进行控制释放。对其控制释放机理进行初步探讨。     

Cu_2 O/PNIPAm温敏复合材料的制备及其缓释性能研究

采用自由基聚合法制备了温敏高分子聚合物PNIPAm,并利用两亲性聚合物在选择性溶剂中的自组装制备出PNIPAm与纳米Cu2O的温敏复合材料;利用红外光谱仪(FT-IR)和紫外-可见吸收光谱仪(UV-Vis)对聚合物的结构和温敏性进行表征,并用扫描电子显微镜(SEM)和激光共聚焦显微镜(LSCM)对复合材料进行结构表征;通过抑菌实验考查温敏复合材料的缓释性能。实验结果表明:制得的PNIPAm凝胶最低临界溶解温度(LCST)约为32.5℃;交联剂摩尔分数(占单体的物质的量)从2%增大到4%时,凝胶溶胀度下降40%;抑菌实验发现,温敏复合材料对氧化亚铜的缓释效果明显。     

H型两亲性嵌段共聚物的合成与表征

以聚乙二醇(PEG-400)、环氧氯丙烷为原料,氢氧化钾为缚酸剂,十六烷基三甲基溴化铵为相转移催化剂制得聚乙二醇缩水甘油醚(epoxide-PEG-epoxide).然后,在氢氧化钠水溶液中,聚乙二醇缩水甘油醚中的环氧键水解生成分子链两端各含有两个羟基的大分子引发剂((HO)2PEG(OH)2).最终,以辛酸亚锡为催化剂,端羟基大分子引发剂引发ε-己内酯开环聚合,合成了不同相对分子质量的H型两亲性嵌段共聚物((PCL)2PEG(PCL)2).通过红外光谱(FTIR)和核磁共振氢谱(1H-NMR),聚乙二醇缩水甘油醚,端羟基大分子引发剂和H型两亲性嵌段共聚物的结构得到了确认.示差扫描量热法对两亲性嵌段共聚物热性能的研究表明:当亲水段的聚乙二醇分子量为400时,聚合物的熔融温度主要受疏水段的聚己内酯影响,随着聚己内酯链段长度的增加,熔融温度升高.     

两亲性聚合物沉积法聚四氟乙烯中空纤维膜的亲水改性研究

以具有两亲结构的两亲性聚合物脂肪醇聚氧乙烯醚，通过回旋振荡涂覆法对疏水的聚四氟乙烯(PTFE)中空纤维膜改性处理制备亲水性聚四氟乙烯膜，在膜表面形成亲水沉积层，并研究了两亲性聚合物浓度、涂覆时间、热处理时间和热处理温度对PTFE中空纤维膜亲水性能的影响。结果表明，两亲性聚合物浓度为5%,涂覆时间2 h,热处理时间和温度分别为16 h和40℃条件下制备的聚四氟乙烯中空纤维膜，纯水通量可达2 482 L/(m²·h)。     

两亲性无规聚合物P(MMA-co-MAA)的合成及其自组装研究

由疏水性单体甲基丙烯酸甲酯(MMA)和亲水性单体甲基丙烯酸(MAA)进行自由基溶液共聚,合成了一系列配比不同的两亲性无规聚合物P(MMA-co-MAA),用红外光谱、核磁共振和凝胶渗透色谱对聚合物结构进行了表征。采用一种操作过程简单、快捷、环保的新方法制备了聚合物胶束,即将一定质量的聚合物溶于碱性水溶液中,通过中和原理进行自组装,并得到球形胶束。通过透射电子显微镜(TEM)和激光光散射(DLS)法,研究了聚合物中基团摩尔比例不同时对胶束形貌和流体动力学半径(Rh)的影响。     

微乳液聚合法AM-SMA疏水缔合聚合物的研究

通过甲基丙烯酸十八酯(SMA)与丙烯酰胺(AM)微乳液聚合合成了疏水缔合聚合物,采用红外光谱(FTIR)表征了疏水缔合聚合物的结构,考察了SMA含量、AM含量、聚合物浓度、NaCl浓度以及剪切速率对疏水缔合聚合物溶液表观粘度的影响。结果表明聚合物水溶液临界缔合浓度为0.6g/dL,疏水缔合聚合物表现出较强的盐增粘效应和抗盐性;12%SMA的疏水缔合聚合物水溶液表现出剪切增粘和假塑性流体行为,FTIR谱图初步证实疏水缔合聚合物的结构。     

聚合物胶束载药体系研究进展

两亲性嵌段共聚物能够在水溶液中通过自组装形成聚合物胶束,其疏水嵌段构成胶束内核,可以有效包载疏水性药物;而亲水嵌段构成胶束外壳,有利于胶束的稳定和体内长循环。聚合物胶束作为药物载体得到了广泛研究,有些已经进入了临床试验和应用阶段。概述了聚合物胶束的特点,介绍了聚合物胶束的组成、载药胶束的制备方法以及聚合物胶束作为药物传递系统的一些实例,并对聚合物胶束载药体系的研究方向进行了展望。     

超临界CO2下三元含氟疏水缔合聚合物的合成及溶液性能研究

设计聚合物的分子结构并在超临界CO2下以丙烯酰胺(AM)、2-甲基-2-丙烯酰胺基丙磺酸(AMPS)及甲基丙烯酸十二氟庚酯(G04)为单体合成三元含氟疏水缔合聚合物,并用FTIR和元素分析对结构进行表征。研究反应温度、压力及引发剂加入量对产物聚合反应转化率及相对分子量的影响,并对三元含氟疏水聚合物浓度对溶液表观粘度的影响进行研究。结果表明:在超临界CO2体系下可制备三元共聚含氟聚合物,且由于含氟疏水基团的存在,该聚合物水溶液具有明显的疏水缔合作用。     

两亲性聚合物分子自组装的研究进展

两亲性聚合物以其同时具有亲水和疏水链段的独特结构,在生物医药、纳米技术等领域有广泛的用途。本文主要介绍了两亲性聚合物通过分子自组装形成聚集体的研究进展,详细论述了几种分子自组装聚集体的制备,包括结构、组成、分子量控制的简单聚集体、半结晶聚集体、交联聚集体以及具有刺激响应性(pH值响应性、温度响应性、pH值/温度双重响应性、氧化还原响应性、溶剂极性响应性等)的智能型聚集体,两亲性聚合物结构的可控性以及如何提高聚集体的稳定性成为国内外专家研究的重点,指出结晶诱导分子自组装及智能型分子自组装是未来研究的热点。     

借助ATRP法合成两亲性星状多臂h-PCMS-g-mPEG接枝共聚物

以对氯甲基苯乙烯(CMS)为活性单体,CuCl/2,2'-联吡啶(bpy)为催化体系,通过原子转移自由基聚合反应(ATRP)合成具有不同结构特征的超支化聚对氯甲基苯乙烯(h-PCMS),分别考查了反应温度、反应时间对所合成的h-PCMS的组成结构、相对分子质量分布指数和转化率的影响。在NaH催化下,以不同支化度的h-PCMS与单甲氧基封端聚乙二醇(mPEG)进行醚化反应,制得以超支化大分子h-PCMS为疏水性核,以单甲氧基封端聚乙二醇(mPEG)为亲水性臂的两亲性星状多臂接枝共聚物h-PCMS-g-mPEG。采用红外光谱(IR)、凝胶色谱(GPC)、核磁共振氢谱(1H-NMR)及差示扫描量热仪(DSC)等技术对聚合物的结构和性能进行表征。     

Temperature-sensitive and highly water-soluble titanate nanotubes

Water-soluble titanate nanotubes (TNTs) with temperature-responsive shells were synthesized by grafting poly(N-isopropylacrylamide) (PNIPAAm) from TNTs via surface atom transfer radical polymerization (ATRP) using ATRP agent functionalized TNTs as macroinitiator. Proton Nuclear magnetic resonance spectroscopy (¹H NMR), Fourier-transform infrared (FT-IR) and thermogravimetric analyses (TGA) results prove the successful graft of PNIPAAm chains from TNTs. TGA shows that the amount of PNIPAAm grown from the TNTs increased with the increase of monomer/initiator ratio. Transmission electron microscope (TEM) measurements displays the obtained TNTs-g-PNIPAAm nanohybrids have a core-shell structure of TNT cores and PNIPAAm shells. In addition, the functional nanotubes demonstrate a reversible low critical solution temperature (LCST) transition with the increase of solution temperature. The synthetic method presented here can also be extended to graft other stimuli responsive polymers from TNTs.     

Star polymers with random number of temperature sensitive arms and crosslinked poly(EGDMA)-core and their application to drug delivery

A simple methodology is described for the preparation of temperature sensitive star polymers with random number of arms and crosslinked core. In the first step, well defined, monodisperse poly(N-isopropylacrylamide) PNIPAAm polymers were prepared by reversible addition–fragmentation chain transfer polymerization (RAFT-polymerization) by using 4-cyanopentanoic acid dithiobenzoate as chain transfer agent (CTA). In the second step, the PNIPAAm polymers were used as macro-CTA’s for copolymerization with ethylene glycol dimethacrylate (EGDMA) by the RAFT-technique. Adjusting the macro-CTA to EGDMA ratio, nanometric star polymers with small or big core could be prepared as revealed by gel permeation chromatography (GPC), dynamic light scattering (DLS) and viscometry. The same methodology was applied for the preparation of star polymers with poly(NIPAAm)-b-poly(hexyl acrylate) arms. The so prepared temperature sensitive multiarm materials are a stable alternative to polymeric micelles as nano-carriers for drug-delivery applications.     

Autoassociative natural polymer derivatives: the alkylchitosans. Rheological behaviour and temperature stability

Chitosan may be chemically modified by reductive amination leading to the grafting of hydrophobic alkyl chains along the hydrophilic macromolecular chain. This allows to obtain amphiphilic polymers whose the hydrophobicity (or the hydrophile-lipophile balance, HLB) may be adjusted according to the length of the grafted alkyl chain or the degree of substitution of the amine functions. The existence of hydrophobic interactions between the alkyl chains will change the physico-chemical properties of the solutions of the modified chitosans. These properties are studied and the study is particularly focused on the influence of the polymer concentration and temperature on them and applications as rheology modifiers. Threshold concentrations, over which the polymer solutions have peculiar temperature behaviour, were defined. According to their structure it is possible to prepare solutions with constant viscosity or increasing one with temperature.     

Thermoviscosifying polymer used for enhanced oil recovery: rheological behaviors and core flooding test

Polymer flooding represents one of the most efficient processes to enhance oil recovery, but the poor thermostability and salt tolerance of the currently used water-soluble polymers impeded their use in high temperature and salinity oil reservoirs. Thermoviscosifying polymers (TVPs) whose viscosity increases upon increasing temperature and salinity may overcome the deficiencies of most water-soluble polymers. A novel TVP was studied in comparison with traditional partially hydrolyzed polyacrylamide (HPAM) in synthetic brine regarding their rheological behaviors and core flooding experiments under simulated high temperature and salinity oil reservoir conditions (T: 85 °C, and total salinity: 32,868 mg/L, [Ca²⁺] + [Mg²⁺]: 873 mg/L). It was found that with increasing temperature, both apparent viscosity and elastic modulus of the TVP polymer solution increase, while those of the HPAM solutions decrease. Such a difference is attributed to their microstructures formed in aqueous solution, which were observed by cryogenic transmission electron microscopy. Core flow tests at equal conditions showed an oil recovery factor of 13.5 % for the TVP solution versus only 2.1 % for the HPAM solution.     

Photo cross-linkable poly(N-isopropylacrylamide) copolymers III: micro-fabricated temperature responsive hydrogels

Micro-fabricated temperature responsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels were produced by photolithographic patterning of photo cross-linkable polymers. These polymers were synthesized by copolymerization of N-isopropylacrylamide (NIPAAm) and 2-(dimethyl maleimido)-N-ethyl-acrylamide (DMIAAm). The patterning process of polymers with 9.2 mol% DMIAAm and film thickness below 5 μm in the dry state was able to depict a lateral resolution of 4 μm with insignificant shape change. In order to increase the adhesion of the swollen hydrogels, and thus, the resolution of a particular pattern, a special adhesion promoter based on a monochlorosilane anchor group and a chromophore head group was synthesized. If a silicon wafer surface was pretreated with the adhesion promoter, the structures were stable and well adhered even at lower cross-linking densities. The hydrogels are suitable as working substances for micro-actuators because of their thermally induced volume changes. The swelling ratio of the pattern at low temperatures increased with a decreased cross-linking density. As expected from the chemical composition of the gels, the phase transition temperature (T_c) decreased with increasing DMIAAm content. The swelling of microstructures in water in comparison to macroscopic objects occured significantly faster. This behavior was attributed to the small gel dimension but it was even more pronounced because of the sponge-like nanostructure of the hydrogels characterized by high-resolution field emission scanning electron microscopy. Suitable applications of these hydrogels are adjusting limbs in fluid micro-systems such as micro-pumps and micro-valves.     

Multi-step precipitation separation system using mixture of thermosensitive polymers

Summary Multi-step precipitation separation system was developed by using aqueous mixtures of some thermosensitive polymers. The following three polymers were used here; poly(N-n-propylacrylamide), poly(N-isopropylacrylamide), and poly(N-isopropylmethacrylamide). A mixture of the three polymers showed three endothermic peaks, and the peak top temperatures were almost consistent with that of the each polymer solution. The polymers were purified by thermal precipitation to obtain fractions which can respond in narrow temperature ranges prior to use. In the case of the precipitation separation of two polymers mixtures, purities of the obtained precipitate and supernatant fractions became high comparing with the case in which the unpurified polymers were used. Parts of the polymers which were not the precipitation targets were also precipitated by the separation procedures. This was caused not only by insolubilization of the non-targeted polymers due to their phase transitions but also by their non-specific entanglement with the targeted polymers. The purities of the fractions also improved when the difference of the phase transition temperature between two polymers was large enough to avoid the coprecipitation. In the case of the precipitation separation of mixtures of the three polymers, purities of each fraction also improved when the purified polymers were used.     

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。     

Polymer microparticles production by supercritical assisted atomization

Supercritical Assisted Atomization (SAA) was used to micronize poly(methyl methacrylate) (PMMA) and poly-l-lactide (PLLA), selected as a model polymers, to verify SAA processability of polymers and the performance of this process.The effect of process parameters such as the mass flow ratio between carbon dioxide and liquid solution, precipitation temperature and solute concentration in the liquid solution were studied to evaluate their influence on morphology and size of precipitated particles.Successful micronization of the polymers was obtained with a narrow particle size distribution. PMMA and PLLA size-controlled microparticles were produced ranging between 0.05 and 1.6 μm and between 0.1 and 3.5 μm, respectively. Both PMMA and PLLA presented a good processability at temperature conditions far from the glass transition temperature, but high enough to allow a fast solvent evaporation.     

Influence of process parameters on ethylene-norbornene copolymers made by using [2,2′-methylenebis(1,3-dimethylcyclopentadienyl)]-zirconium dichloride and MAO

Ethylene-norbornene copolymerization was investigated by using metallocene catalysts, [2,2′-methylenebis( 1,3-dimethylcyclopentadienyl)]zirconium dichloride(2,2′-CH₂ (1,3-Me₂Cp)₂ZrCl₂, Catalyst A) and racemicethylenebis( indenly)zirconium dichloride (rac-Et(Ind)₂ ZrCl₂, Catalyst B), in the presence of methylaluminoxane as a cocatalyst. The influences of different process parameters such as polymerization temperature and ethylene pressure were studied by using a 56 wt% norbornene solution in toluene. The results show that Catalyst A has a higher activity in copolymerization than Catalyst B. Catalyst A also has a superior norbornene insertion performance to Catalyst B, resulting in polymers with higher glass transition temperatures, by approximately 70 ‡C, at similar polymerization conditions, indicative of a great commercial potential of Catalyst A.     

Thermosensitive and hydrolysis‐sensitive poly(organophosphazenes)

The lower critical solution temperature (LCST) properties and hydrolytic behaviour of thermosensitive biodegradable polyphosphazenes with monomethoxy‐poly(ethylene glycol), glycine ethyl ester and depsipeptide ethyl esters substituents have been studied. All the polymers synthesized show LCST properties. The LCSTs of the polymers are affected by the composition of the polymers and increase with the degradation of the polymers in aqueous solution. The higher content of depsipeptide ethyl esters in the polymers accelerates the LCST change and the degradation of the polymers in aqueous solution. Most polymers synthesized have half‐lives of less than 10 days in neutral solution. © 2002 Society of Chemical Industry