N,N-二乙基丙烯酰胺与丙烯酸在聚丙烯薄膜表面光接枝制备二元接枝膜及其温度、pH值敏感特性研究

以二苯甲酮为引发剂,聚丙烯薄膜(CPP)为基材,通过紫外光接枝的方法制备了具有温度和pH值双重敏感特性的聚N,N-二乙基丙烯酰胺(PNDEA)与聚丙烯酸(PAA)二元接枝膜.在PNDEA一次接枝膜的制备过程中,引发剂与单体配比相同时,本体接枝方法的接枝速率在反应初期明显高于溶液接枝方法;采用溶液法时,增大引发剂与单体配比等可提高接枝率.用本体法所制得的PNDEA一次膜光活化接枝PAA时接枝速率较溶液法高,并且能够实现较高的PAA接枝率.用红外光谱(FTIR)、X射线光电子能谱化学分析(ESCA)对接枝层组成的表征结果证实了二元接枝层的存在.在不同温度下,PNDEA一次接枝膜的FTIR谱图中酰胺Ⅰ带特征吸收峰发生位移表明它具有温度敏感特性.用扫描电子显微镜(SEM)对PNDEA接枝层表征结果表明,用不同接枝手段所制备的接枝膜具有不同的表面形貌.通过吸水率测定研究了二元接枝膜的温度及pH值敏感特性.     

N,N-二乙基丙烯酰胺与丙烯酸在聚丙烯薄膜表面光接枝制二元接枝膜及其温度、pH值敏感特性研究

以二苯甲酮为引发剂,聚丙烯薄膜(CPP)为基材,通过紫外光接枝的方法制备了具有温度和pH值双重敏感特性的聚N,N-二乙基丙烯酰胺(PNDEA)与聚丙烯酸(PAA)二元接枝膜.在PNDEA一次接枝膜的制备过程中,引发剂与单体配比相同时,本体接枝方法的接枝速率在反应初期明显高于溶液接枝方法;采用溶液法时,增大引发剂与单体配比等可提高接枝率.用本体法所制得的PNDEA一次膜光活化接枝PAA时接枝速率较溶液法高,并且能够实现较高的PAA接枝率.用红外光谱(FTIR)、X射线光电子能谱化学分析(ESCA)对接枝层组成的表征结果证实了二元接枝层的存在.在不同温度下,PNDEA一次接枝膜的FTIR谱图中酰胺Ⅰ带特征吸收峰发生位移表明它具有温度敏感特性.用扫描电子显微镜(SEM)对PNDEA接枝层表征结果表明,用不同接枝手段所制备的接枝膜具有不同的表面形貌.通过吸水率测定研究了二元接枝膜的温度及pH值敏感特性.     

聚氨酯微球的接枝改性及温敏特性

以N-异丙基丙烯酰胺(NIPAAm)为单体, 二苯甲酮(BP)为光敏剂, 过硫酸胺(APS)为自由基引发剂, 采用溶液中光接枝方法制备了具有温度敏感特性的聚氨酯微球(PUS). 傅里叶变换红外光谱(FTIR)和扫描电子显微镜(SEM)结果表明, 在聚氨酯微球表面形成了聚异丙基丙烯酰胺(PNIPAAm)接枝聚合物层. 在接枝过程中, 延长反应时间与增加引发剂浓度均有利于提高接枝率. 常温下, 接枝率随反应时间延长呈线性增长, 当反应时间超过40 min后, 接枝率基本保持稳定; 而引发剂浓度对接枝率的影响存在最佳优化值, 即其浓度为单体质量分数的3%. 采用差示扫描量热法(DSC)对接枝改性前后聚氨酯微球的温敏特性进行分析表征, 证实改性后的微球在35 ℃左右出现低临界互溶温度(LCST), 在此温度附近表现出对温度敏感特性. 接触角测试与溶胀测试结果表明, 在低临界互熔温度以下, 接枝改性的聚氨酯微球具有良好的亲水性.     

紫外光引发LDPE膜接枝含氟丙烯酸酯的研究

通过紫外光引发表面接枝聚合反应的方法 ,把含氟丙烯酸酯单体R 5 6 1 0引到LDPE薄膜上 .对经丁酮抽提后的接枝膜进行FTIR、ESCA、SEM和DSC等表征 ,证实含氟聚合物以化学键的方式接枝在LDPE基体膜上 .在一定范围内 ,增加紫外光强、引发剂和单体浓度以及反应温度等均有利于提高接枝率 .经计算R 5 6 1 0的紫外光引发接枝聚合反应总活化能为 5 4 2kJ mol.接枝膜的接触角随着接枝率的提高逐步增大 ,直至趋于恒定 .作者提出接枝膜存在一个在接触角测定时影响基体膜与探测水滴相互作用过程的边界层 .当接枝率较低、接枝层厚度小于边界层临界厚度时 ,基体LDPE影响接触角的大小 ,但随着接枝率提高 ,接枝层逐渐变厚 ,氟聚合物层对接触角的贡献逐渐占优势 ,导致接触角随之增大 .当接枝率超过一定值以后 ,接枝层厚度超过边界层临界厚度 ,接枝层对接枝膜的接触角起全部贡献 ,接触角测定值随之稳定     

PET表面接枝偶氮聚合物和光致取向研究

合成了一种丙烯酸酯类含芳香族偶氮生色团的单体ANB .以二苯甲酮为引发剂 ,采用固相紫外光接枝方法将上述单体接枝到聚酯 (PET)膜的表面 ,得到了一种具有光响应性的接枝膜 .通过SEM研究了接枝膜的表面和断面的形貌 ,观察到偶氮接枝层均匀地覆盖了PET表面 ,接枝层厚度约 0 4μm .研究发现 ,当使用488nm的线偏振激光照射接枝膜时 ,偶氮生色团通过快速的顺反异构化反应在垂直于偏振光极化方向上发生取向 ,得到了具有光学各向异性表面的PET接枝膜 .接枝膜的取向是一个快速过程 ,取向有序度参数在 2min时即达到最大值 ,为 0 0 6左右     

芴酮引发光接枝改性LDPE膜的研究

采用紫外光引发接枝表面改性的方法,以芴酮(FL)为引发剂,在低密度聚乙烯(LDPE)薄膜表面上接枝丙烯酸(AA)、甲基丙烯酸(MAA)、丙烯酸甲酯(MA)、甲基丙烯酸甲酯(MMA)、丙烯酰胺(AM)等单体,以赋予薄膜表面新的化学性质.考察了引发剂浓度、紫外光的辐照时间、辐照强度、单体种类对LDPE薄膜接枝程度的影响.结果表明,在一定范围内,增加芴酮浓度,可以提高单体的接枝率,但当芴酮浓度达到5%时,接枝率反而下降.延长辐照时间至4 min和提高紫外光的辐照强度达100 W/m2,均有利于接枝反应的进行.不同单体在LDPE膜上的接枝能力与单体的活性、单体与基材的相容性等因素有关.接枝后,LDPE与水的接触角下降程度不仅与单体在膜上的接枝量有关,还与接枝单体的亲水性能密切相关.     

在聚砜膜表面接枝聚甲基丙烯酸及接枝膜对生物碱化合物的吸附特性

首先将聚砜(PSF)氯甲基化,制得氯甲基化聚砜(CMPSF),CMPSF流延成膜后与乙二胺(EDA)反应,制得表面键合有EDA的氨基化膜(AMPSF)。在此基础上,在水溶液体系中构建氨基-过硫酸盐表面引发体系,使甲基丙烯酸(MAA)发生接枝聚合,制得了功能接枝膜PSF-gPMAA。考察了影响膜接枝过程的主要因素,优化了接枝聚合条件。采用傅里叶红外光谱(FTIR)、光学显微镜(OM)及称重法对接枝膜PSF-g-PMAA进行了表征。最后研究了功能接枝膜对氧化苦参碱和金雀花碱两种生物碱化合物的吸附特性。结果表明,采用氨基-过硫酸盐表面引发体系,可以顺利地实施MAA在PSF膜表面的接枝聚合,接枝度随氨基化膜AMPSF表面氨基键合量的增大而增大,接枝聚合适宜的温度为50℃,溶液中适宜的过硫酸盐用量为单体质量的1.0%。在适宜的条件下可制得PMAA接枝度为4.62mg/cm2的接枝膜。凭借强静电相互作用和氢键作用的协同作用,功能接枝膜PSF-g-PMAA对生物碱化合物可产生强烈的吸附作用,在中性溶液中,对氧化苦参碱和金雀花碱的吸附容量分别可达277μg/cm2和331μg/cm2。     

RAFT链转移剂存在下凹凸棒土表面甲基丙烯酸甲酯接枝聚合

将γ-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPS)接枝到凹凸棒土(AT)表面,制得表面带有可聚合碳碳双键的改性粒子AT-MPS;以二硫代苯甲酸氰基异丙酯(CPDB)为链转移剂,采用可逆加成断裂链转移(RAFT)聚合技术,在AT表面进行甲基丙烯酸甲酯(MMA)接枝聚合.通过红外(FTIR)、热失重(TGA)等方法进行了表征,考察了引发剂以及RAFT链转移剂用量对聚合反应动力学和AT表面接枝聚合接枝率的影响.结果表明,PMMA通过RAFT聚合成功接枝在AT表面;基于RAFT过程的接枝聚合比传统自由基接枝聚合具有更长的反应时间和较高的接枝率.本体系相对适宜条件:温度为70℃,[MMA]/[CPDB]/[AIBN]为400/1/0.5.此条件下聚合反应具有很好的可控性,溶液中的聚合物分子量分布指数为1.2~1.3,AT表面PMMA接枝率为16.33%.引发剂和RAFT链转移剂用量过大均会造成接枝率降低.     

纳米SiO2锚固光敏基团引发MMA光接枝聚合研究

对纳米SiO2进行了锚固光引发剂的表面修饰,进而引发甲基丙烯酸甲脂(MMA)光接枝聚合制备有机/无机复合粒子.纳米SiO2粒子首先用氯化亚砜进行表面氯化,再与光引发剂2-羟基-4-(2-羟基乙氧基)-2-甲基苯丙酮(Irgacure2959)反应从而锚固上光引发剂.通过紫外光引发MMA在经过修饰过的纳米SiO2表面上进行表面光接枝聚合.采用IR、TGA和TEM等方法表征了接枝前后纳米粒子的变化,证明了表面接枝物的存在,并研究了不同反应条件对单体转化率、接枝率和接枝效率的影响.研究结果表明,搅拌对接枝过程的影响比较显著.TGA结果显示未搅拌聚合时接枝率只能达到比较小的程度,而在搅拌条件下180min内MMA的接枝率可达到110%.     

表面引发接枝聚合法制备凹凸棒土/聚甲基丙烯酸甲酯杂化粒子的研究

将γ-氨丙基三乙氧基硅烷(APTES)接枝到凹凸棒土(AT)表面,制得表面键合伯氨基的改性粒子AT-APTES;通过AT-APTES表面的伯氨基和过硫酸铵(APS)构成氧化-还原引发体系,采用无皂乳液法实现甲基丙烯酸甲酯(MMA)在AT表面接枝聚合,制得最高接枝率为29.4%的杂化粒子AT-g-PMMA;采用红外光谱(FTIR)、拉曼光谱(Raman)、透射电镜(TEM)以及热失重分析(TGA)等方法对杂化粒子AT-g-PMMA进行了表征;研究了主要配方及工艺条件对表面引发接枝聚合接枝率的影响.结果表明,伯氨基-过硫酸铵引发体系可以有效引发MMA在AT表面接枝聚合,由于引发点位于AT表面,故接枝率较高.本研究体系适宜的温度为65℃,单体MMA用量为水质量的6%,APS用量为单体质量的1%,此工艺条件下可有效减小均聚反应对接枝聚合反应的影响.先接枝到AT表面的聚合物对后续的接枝聚合反应产生抑制作用,接枝率越高,抑制作用越大.     

Controlled pore functionalization of poly(ethylene terephthalate) track-etched membranes via surface-initiated atom transfer radical polymerization

A new method for surface-initiated atom transfer radical polymerization (ATRP) on the technical polymer poly(ethylene terephthalate) (PET) has been developed which allows controlling and estimating the layer thickness of the grafted polymer in the isocylindrical pores of track-etched membranes. After PET surface treatment by oxidative hydrolysis, the bromoalkyl initiator was immobilized on the PET surface in a two-step solid-phase reaction; the isoporous membrane structure was preserved, and the pore diameter was increased from 760 to 790 nm. Poly(N-isopropylacrylamide) (PNIPAAm) was grafted under ATRP conditions from a methanol/water mixture at room temperature. Both monomer concentration and reaction time could be used as parameters to adjust the degree of grafting. Effective grafted layer thickness and its response to temperature were estimated from pure water permeability. All data, especially the high polymer densities (0.37 g/cm3) in the swollen layers at 25 degrees C, indicate that grafted PNIPAAm with a "brush" structure has been achieved. For dry PNIPAAm layer thicknesses on the PET pore walls of up to 80 nm, a temperature-induced swelling/deswelling ratio of approximately 3 had been observed. Reduction of the brush grafting density, via composition of the reaction mixture used in solid-phase synthesis for initiator immobilization, led to an increase of that swelling/deswelling ratio. Further, density and temperature response of the grafted PNIPAAm layers synthesized via ATRP were compared with those obtained in the same membranes by less controlled photografting, leading to lower grafting density and larger gradients in grafted layer density and, consequently, much higher swelling/deswelling ratios (>15).     

Radiation-induced grafting of N-isopropylacrylamide onto the brominated poly(2,6-dimethyl-1,4-phenylene oxide) membranes

A novel thermo-sensitive switching membrane has been prepared by radiation-induced simultaneous grafting N-isopropylacrylamide (NIPAAm) onto brominated poly(2,6-dimethyl-1,4-phenylene oxide) BPPO. In order to attain a high grafting degree, the effects of dose, dose rate, concentration of NIPAAm, concentration of inhibitor Cu²⁺, membrane thickness and solvents were investigated. The grafting process was characterized by FTIR spectroscopy and the highest grafting degree obtained was 7.87%. The thermo-sensitive property of the grafted membrane was measured by water flux (20–48 °C). The results showed that the grafted membrane could respond instantly to environmental temperature changes, and there was a sharp change around the lower critical solution temperature as it is normally seen in PNIPAAm hydrogel.     

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.     

Preparation of Thermal-responsive Chitosan-graft-N-isopropylacrylamide Membranes via γ-Ray Irradiation

A novel thermo-sensitive switching membrane has been prepared by radiation-induced simultaneous grafting N-isopropylacrylamide （NIPAAm） onto chitosan membrane. Fourier transform infrared spectroscopy （FTIR） was used to identify the structure of the grafted membranes. The surface morphology of the grafted membrane was observed from scanning electron microscopy （SEM）. Pure water flux measurements showed that water flux of the grafted membrane decreased with the increase of temperature, while that of chitosan membrane was constant. It was proved that grafted membrane was sensitive to temperature.     

Surface modification of polyolefins by photografting of acrylic monomers

High-speed surface modification of polypropylene (PP) and polyethylene (PE) films has been achieved by liquid phase photograft polymerisation of acrylic acid (AA) and hydroxypropyl acrylate (HPA). Benzophenone was used as photoinitiator to generate polymer radicals at the surface of the polyolefin film. The grafting reaction was carried out in aqueous solution or with the neat monomer, which was laminated between two PP films, in the presence of air. Under the intense illumination of a UV-curing line, acrylic acid was grafted within seconds to polypropylene films or fabrics, which were thus made hydrophilic. Direct evidence of surface grafting was obtained through infrared spectroscopy analysis and surface energy measurements. This continuous photografting process proved to be very efficient to improve the adhesion of UV-cured acrylate coatings on polyolefin-made materials.     

SEM研究PET核孔膜的光接枝聚合

以PET核孔膜为基材 ,二苯甲酮为引发剂 ,采用光接枝方法实现了丙烯酸和丙烯酰胺在核孔膜上的接枝 ,用扫描电镜 (SEM)直接观察了接枝前后膜的表面形貌 ,考察了不同因素对于接枝位置和接枝效果的影响 .发现膜材料本身特性和接枝反应条件对接枝位置和接枝效果有较大影响 .通过光接枝能够实现膜孔的封盖、缩小、填堵等不同的效果 .采用正侧涂布法反应 ,标准直孔 ,特别是小孔径膜 (0 4 μm) ,不利于孔内的接枝 ,接枝主要在膜的表面 ,从而产生孔封盖效应 .双锥形的非标准直孔 ,由于孔壁的受光性好 ,容易发生孔壁上的接枝从而被填充 .大孔径的膜 (5 μm) ,需要加入交联剂才能在孔壁上形成厚的接枝层 .提出了一种新的反应方法 背侧吸附法 ,反应液依靠毛细作用由膜的底部吸入膜孔 ,膜的向光侧表面不存在反应液 ,接枝只发生在膜孔内 ,从而得到很好的填孔效果 .     

Azobenzene-containing molecularly imprinted polymer microspheres with photo- and thermoresponsive template binding properties in pure aqueous media by atom transfer radical polymerization

A facile, general, and highly efficient approach to obtain azobenzene (azo)-containing molecularly imprinted polymer (MIP) microspheres with both photo- and thermoresponsive template binding properties in pure aqueous media is described for the first time, which involves the first synthesis of "living" azo-containing MIP microspheres with surface-immobilized alkyl halide groups via atom transfer radical precipitation polymerization (ATRPP) and their subsequent modification via surface-initiated atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm). The successful grafting of poly(NIPAAm) (PNIPAAm) brushes onto the obtained MIP microspheres was confirmed by FT-IR, SEM, water dispersion stability and static contact angle studies, and template binding experiments. The introduction of PNIPAAm brushes onto the azo-containing MIP microspheres significantly improved their surface hydrophilicity and imparted thermoresponsive properties to them, leading to their pure water-compatible and thermoresponsive template binding properties. In addition, the binding affinity of the imprinted sites in the grafted azo-containing MIP microspheres was found to be photoresponsive toward the template in pure water, and this photoregulation process proved to be highly repeatable under photoswitching conditions.     

Grafting of temperature sensitive PNIPAAm on hydrophilised polysulfone UF membranes

Poly(N-isopropyl acrylamide) (PNIPAAm) was grafted on a polysulfone UF membrane. The changes of permeability as well as retention of PEG (35 kg/mol) and Dextran (500 kg/mol) between 23 and 60 °C were determined for both grafted and unmodified membranes. The results showed that the viscosity corrected water permeability and solute retention were almost constant for the unmodified membranes within the measured temperature range, the permeability of the grafted membranes increased and the retention of Dextran and PEG decreased with temperature. The variation of changes was most obvious in the temperature range 27–37 °C for the modified membranes due to the lower critical solution temperature (LCST) of PNIPAAm. The location and profile of PNIPAAm inside and on the surface of the membrane were analysed by SEM and FTIR. Depth profile calculation for FTIR spectra showed that PNIPAAm was mostly placed inside the membrane (at a depth of 1.06–1.10 μm from the surface) rather than on the surface. The amount of grafted PNIPAAm was low and did not significantly affect the morphology of the membrane. Therefore, a difference in SEM pictures of modified and unmodified membranes could not be seen. The modified membrane exhibited a clearly different thermal response compared to the unmodified one.