采用巯基-BPO氧化还原引发体系实现GMA在硅胶微粒表面的高效接枝聚合

使用偶联剂γ-巯丙基三甲氧基硅烷(MPMS,KH-590),对微米级硅胶微粒进行了表面化学改性,制得了表面带有巯基的改性微粒MPMS-SiO2.使改性微粒MPMS-SiO2表面的巯基与溶液中的BPO构成氧化-还原引发体系,实现了油溶性单体甲基丙烯酸缩水甘油酯(GMA)在硅胶微粒表面的引发接枝聚合,制得了接枝度为26g/100g的接枝微粒PGMA/SiO2.采用红外光谱(FTIR)、扫描电镜(SEM)及热重分析(TGA)等方法对接枝微粒PGMA/SiO2进行了表征。在此基础上,重点研究了主要因素对巯基-BPO体系引发GMA接枝聚合的影响.研究结果表明,巯基-BPO体系引发的接枝聚合,由于活性位点位于固体表面,因此也是一种表面引发接枝法。与在固体微粒表面引入可聚合双键的"穿过接枝"("grafting through")法相比,巯基-BPO引发体系可更有效地实现油溶性单体的接枝聚合.为制得高接枝度的接枝微粒PGMA/SiO2,适宜的温度为55℃,适宜的BPO用量为单体的1wt%左右,适宜的单体浓度为10 wt%。     

构建芳叔胺-BPO氧化还原引发体系实现苯乙烯在硅胶微粒表面的高效接枝聚合

首先使用偶联剂γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行了表面改性,制得表面带有伯胺基的改性微粒SiO2-AMPS,接着使4-(二乙氨基)水杨醛(DEAS)与微球SiO2-AMPS发生席夫碱反应,制得表面含有芳叔胺基的改性微粒SiO2-DEAS.使改性微粒SiO2-DEAS表面的芳叔胺基团与溶液中的BPO构成氧化-还原引发体系,实现了油溶性单体苯乙烯(St)在硅胶微粒表面的引发接枝聚合,制得了高接枝度(27 g/100g)的接枝微粒SiO2-DEAS-g-PSt.采用红外光谱(FTIR)、扫描电镜(SEM)及热重分析(TGA)等方法对接枝微粒SiO2-DEAS-g-PSt进行了表征.在此基础上,重点研究了主要因素对芳叔胺-BPO体系引发St接枝聚合的影响.研究结果表明,与在固体微粒表面引入可聚合双键的"穿过接枝"(grafting through)法相比,芳叔胺-BPO体系引发的接枝聚合,由于活性位点位于载体表面,故具有高的接枝度,是油溶性单体的一种高效率的表面引发接枝法.为制得高接枝度的接枝微粒SiO2-DEAS-g-PSt,适宜的温度为50℃,适宜的BPO用量为单体的3 wt%左右,适宜的单体浓度为10 wt%.     

氨基-铈盐氧化还原体系引发对苯乙烯磺酸钠在硅胶微粒表面的接枝聚合

使用偶联剂γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行表面化学改性,将氨基引入硅胶微粒表面,构成氨基-Ce(Ⅳ)盐氧化-还原引发体系。研究了在其作用下对苯乙烯磺酸钠(SSS)在硅胶微粒表面的接枝聚合,制得了具有较高接枝度(18g/100g)的接枝微粒PSSS/SiO2。采用FTIR、SEM及TGA等方法对接枝微粒进行表征。考察了对该表面引发接枝聚合体系接枝度影响的主要因素。结果表明,氨基-Ce(Ⅳ)盐体系可以有效地引发乙烯基单体在固体微粒表面的接枝聚合,氨基的质子化对产生自由基的引发步骤具有负影响;为提高PSSS的接枝度,引发剂溶液(铈盐+硫酸)宜采用滴加的方式加入;适宜的单体浓度为14(wt)%;接枝聚合宜在50℃下进行。接枝微粒PSSS/SiO2是一种功能复合微粒,凭借离子交换作用,对重金属离子和稀土离子均可产生强的吸附作用。     

构建巯基-Ce(Ⅳ)盐氧化还原引发体系实现丙烯腈在硅胶微粒表面的高效接枝聚合

使用偶联剂γ-巯丙基三甲氧基硅烷(MPMS,KH-590),对微米级硅胶微粒进行了表面化学改性,将巯基引入硅胶微粒表面(SiO2-MPMS),构成巯基-Ce(Ⅳ)盐氧化-还原引发体系,探索研究了丙烯腈在硅胶微粒表面的引发接枝聚合,制得了高接枝度(30 g/100g)的接枝微粒SiO2-MPMS-g-PAN.采用红外光谱(FTIR)、扫描电镜(SEM)及热重分析(TGA)等方法对接枝微粒SiO2-MPMS-g-PAN进行了表征.在此基础上,重点研究了主要因素对巯基-Ce(Ⅳ)盐体系引发AN接枝聚合的影响.研究结果表明,类似于羟基-Ce(Ⅳ)盐体系,巯基-Ce(Ⅳ)盐体系也可以有效地引发乙烯基单体在固体微粒表面接枝聚合.与在固体微粒表面引入可聚合双键的"grafting through"接枝聚合法相比,铈盐引发的接枝聚合,由于活性位点居于载体表面,故具有高的接枝度,是一种高效率的表面引发接枝法.为制得高接枝度的接枝微粒SiO2-MPMS-g-PAN,本研究体系适宜的酸浓度为0.25 mol/L;Ce(Ⅳ)盐浓度为5.0×10-3 mol/L;接枝聚合宜在50℃下进行.     

表面引发接枝聚合法制备接枝微粒PHEMA/SiO2及其8-羟基喹啉功能化转变研究

通过用表面引发接枝聚合和高分子反应制备8-羟基喹啉型复合螯合微粒.首先使用γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行表面改性,制得改性微粒AMPS-SiO2;使改性微粒AMPS-SiO2表面的氨基与溶液中的过硫酸盐构成氧化-还原引发体系,实施了甲基丙烯酸羟乙酯(HEMA)在硅胶微粒表面的高效引发接枝聚合,制得了接枝微粒PHEMA/SiO2.又以5-氯甲基-8-羟基喹啉(CHQ)为试剂,使接枝的PHEMA发生大分子反应,实现了接枝微粒PHEMA/SiO2的8-羟基喹啉功能化转变,制得了复合微粒HQ-PHEMA/SiO2.采用多种手段对两种微粒进行了表征,重点研究了氨基-过硫酸盐表面引发接枝体系的接枝聚合机理,并研究了CHQ与接枝PHEMA的醇羟基之间取代反应的机理,还初步考察了功能微粒HQ-PHEMA/SiO2对重金属离子的螯合吸附性能.研究结果表明,氨基-过硫酸盐表面引发接枝聚合体系具有很高的引发活性,在室温(30℃)即可制得高接枝密度(40 g/100g)的接枝微粒PHEMA/SiO2;CHQ与接枝PHEMA的醇羟基之间的取代反应遵循SN1的反应历程,使用强极性溶剂有利于反应的进行.微粒HQ-PHEMA/SiO2对重金属离子呈现很强的螯合吸附能力,是一种功能复合微粒.     

铈盐引发丙烯腈在含醇羟基硅胶表面的接枝聚合

将偶联剂γ-(2,3-环氧丙氧基)丙基三甲氧基硅烷(EPPS)键合于硅胶微粒表面,在酸性催化剂作用下,键合EPPS的环氧键开环,产生了醇羟基(HXYG),形成表面带有醇羟基的改性微粒HXYG-SiO2.使用铈盐与硅胶表面的醇羟基构成氧化还原引发体系,在硅胶表面实施了丙烯腈的接枝聚合,制备了接枝微粒PAN-SiO2,考察了接枝聚合的影响因素.实验结果表明:在所形成的氧化还原引发体系中,由于初级自由基即引发物种处于硅胶微粒表面,所制备的接枝微粒PAN-SiO2具有高的接枝度(0.19 g/g),且单体的整体接枝效率高;引发剂铈盐的浓度对接枝度有较大的影响,铈盐浓度过大,将会促进氧化终止过程,降低接枝度,适宜的铈盐浓度为5.93×10-3mol/L;接枝度随硫酸浓度的增大呈现先增大后减小的变化规律,当H+离子浓度为0.38mol/L时,PAN的接枝度最高.     

阳离子功能接枝微粒QPDMAEMA/SiO_2的制备及其对阿魏酸吸附特性的研究

使含有氨基的改性硅胶微粒表面的氨基与溶液中的过硫酸盐构成氧化-还原引发体系,实施了甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面的引发接枝聚合,制得接枝微粒PDMAEMA/SiO2;又以氯乙胺为试剂,使接枝的大分子PDMAEMA的叔胺基团发生季铵化反应,实现了接枝微粒PDMAEMA/SiO2的季铵化(Quaternization)转变,制得了阳离子性功能接枝微粒QPDMAEMA/SiO2。采用红外光谱(FTIR)、扫描电子显微镜(SEM)及Zeta电位测定等多种手段对两种微粒进行了表征。主要研究了温度对接枝聚合和季铵化转变反应的影响,优化了反应条件。还考察了功能接枝微粒QPDMAEMA/SiO2对阿魏酸的子吸附性能。研究结果表明,采用-NH2//S2O82-表面引发体系,可有效地实现DMAEMA的接枝聚合,适宜的反应温度为35℃;氯乙胺与接枝微粒叔胺基团之间的季铵化反应可顺利进行,适宜的反应温度为60℃,叔胺基团的季铵化度可达82%。凭借主-客体之间的强静电相互作用并协同以阳离子-π相互作用,功能接枝微粒QPDMAEMA/SiO2对阿魏酸可产生很强的吸附作用,在中性条件下,吸附容量高达187mg/g。     

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.     

接枝型偕胺肟树脂/SiO_2功能复合微粒的制备

用偶联剂γ-(甲基丙烯酰氧)丙基三甲氧基硅烷(KH-570)对微米级硅胶进行了表面化学改性,采用溶液聚合法,在改性硅胶微粒表面接枝丙烯腈(AN),制备了接枝微粒PAN/SiO2。用盐酸羟胺对接枝PAN进行偕胺肟(AO)化转变,制得了接枝有偕胺肟树脂(PAO)的复合型功能微粒PAO/SiO2。采用红外光谱(FT-IR)、热失重(TGA)及扫描电子显微镜(SEM)等测试技术,对接枝微粒PAN/SiO2以及功能微粒PAO/SiO2进行了表征,考察了制备条件对AN的接枝聚合过程及对PAN的偕胺肟化转变过程的影响规律。结果表明,适宜的接枝聚合条件为:引发剂质量分数为1.5%,反应温度为75℃。接枝聚合5h可制得接枝度为0.14g/g的接枝微粒PAN/SiO2。受偕胺肟基团空间位阻的影响,PAN的偕胺肟化转变反应不能进行彻底,适宜的PAN/SiO2偕胺肟化转变反应条件为:介质pH值为6～7,温度70℃,反应时间4h。所制得的功能微粒PAO/SiO2腈基转化率约为78%。     

表面引发接枝聚合法制备抗蚜威分子表面印迹材料及其分子识别与结合特性研究

基于表面引发接枝聚合,设计与建立了一种新的分子表面印迹(MIP)方法.先使用偶联剂γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行表面改性,制得改性硅胶AMPS-SiO2;在酸性水溶液体系中,凭借强静电相互作用,阴离子单体对苯乙烯磺酸钠(PSSS)被结合在模板分子抗蚜威周围;改性硅胶AMPS-SiO2表面的氨基与溶液中的过硫酸盐构成氧化还原引发体系,在硅胶微粒表面产生自由基,引发结合在模板分子周围的SSS及交联剂甲基双丙烯酰胺(MBA)在硅胶微粒表面发生接枝交联聚合,从而实现了抗蚜威分子的表面印迹,制得了抗蚜威分子表面印迹材料MIP-PSSS/SiO2.以残杀威为对比物,采用静态与动态两种方法,考察研究了分子表面印迹材料MIP-PSSS/SiO2对抗蚜威的分子识别特性与结合性能.研究结果表明,印迹材料MIP-PSSS/SiO2对抗蚜威分子具有特异的识别选择性与优良的结合亲和性,相对于残杀威分子,MIP-PSSS/SiO2对抗蚜威分子的识别选择性系数为9.373,显示出高的分子识别选择性.     

Preparation of a sorbitol methacrylate grafted silica as stationary phase for hydrophilic interaction chromatography

A new highly hydrophilic stationary phase based on graft polymerization of sorbitol methacrylate from the surface of Kromasil silica particles is described. Polymerization was initiated by thermal cleavage of tert-butyl hydroperoxide covalently attached to the silica particle surface. Due to the highly amphiphilic properties of the monomer, an extensive search was needed to find solvent conditions that enabled surface-initiated polymerization. This was finally solved by using a mixture of solvents that only partially dissolved the monomer. The graft polymerization was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The resulting stationary phase was evaluated by HPLC and exhibited a selectivity markedly different from that of commercially available columns and of neat silica.     

Surface modification of silica nanoparticles by UV-induced graft polymerization of methyl methacrylate

In this study we modified the surface of silica nanoparticles with methyl methacrylate by UV-induced graft polymerization. It is a surface-initiated polymerization reaction induced by ultraviolet irradiation. The resulting organic-inorganic nanocomposites were near-monodisperse and fabricated without homopolymerization of the monomer. Substantial increase in mean particle size was observed by SEM image analysis after UV-induced grafting of methyl methacrylate onto pure silica particles. FT-Raman spectroscopy and X-ray photoelectron spectroscopy studies of these materials revealed the successful grafting of methyl methacrylate onto the silica surface. The formation of a covalent bond between the grafted PMMA chains and silica surface was indicated by FT-Raman spectra. Thermogravimetric analysis of the PMMA-grafted silica particles indicated the polymer contents in good agreement with SEM photographs.     

Surface-initiated living radical polymerization from silica particles functionalized with poly(ethylene glycol)-carrying initiator

A novel yet versatile approach is described for surface-initiated living radical polymerization (SI-LRP) from silica particles (SiPs). Monodisperse SiPs were surface-modified with a newly designed surface-fixable initiator (BPEGE) having three components: a triethoxysilane moiety, a poly(ethylene glycol) (PEG) unit, and an initiation site for atom transfer radical polymerization (ATRP) in the form of a 2-bromoisobutyryl group. The surface-initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the BPEGE-fixed SiPs. The polymerization proceeded in a living manner, producing SiPs coated with well-defined poly(MMA) of a target molecular weight with a graft density as high as 0.5 chains/nm². Thanks to the amphiphilic property of PEG, the system was successfully applied for SI-ATRP of PEG methacrylate and sodium p-styrenesulfonate in aqueous media in which the BPEGE-fixed SiPs were highly dispersed without causing any aggregations. The formation of colloidal crystals with the polymer brush-afforded SiPs demonstrated the high uniformity and perfect dispersibility of the hybrid particles.     

Graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel by gamma-ray irradiation

Poly(methylvinylsiloxane)-bonded silica gel was synthesized by condensation reaction between silica gel and the hydrolysis product of methylvinyldichlorosilane. Graft polymerization of styrene or indene onto poly(methylvinylsiloxane)-bonded silica gel was carried out by gamma-ray irradiation and compared with that onto silica gel. Homopolymer was found to be formed through a radical mechanism concurrently with an ionic mechanism in the graft polymerization. Probably genuine graft polymers are formed in the graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel, while the product formed in the graft polymerization onto silica gel may be apparent graft polymers.     

Synthesis of a novel restricted access chiral stationary phase based on atom transfer radical polymerization and click chemistry for the analysis of chiral drugs in biological matrices

A novel chiral restricted access material was synthesized via a combination of atom transfer radical polymerization (ATRP) and click chemistry. Poly(2-methyl-3-butyn-2-ol methacrylate) (pMBMA) was grafted onto porous silica gel by a surface-initiated ATRP in order to synthesize an inner layer for β-cyclodextrin (β-CD) immobilization. The azide-modified β-CD was bound to pMBMA by click chemistry. The results demonstrate that click chemistry provides an effective route for the immobilization of β-CD for chiral discrimination. A second ATRP reaction was then used to graft external poly(glycidyl methacrylate) (pGMA) layer onto the silica gel. The external hydrophilic layer was subsequently created by hydrolysis of the epoxy groups of the pGMA. This bi-layer grafted material exhibited both enantioseparation and protein exclusion. It can be used for the efficient separation of chiral compounds in biological samples with direct injection into an HPLC system.     

阴离子型接枝微粒PDAC/PSA的制备及对谷氨酸的吸附性能初探

采用自由基聚合法在溶液聚合体系中将功能单体丙烯酰氧乙基三甲基氯化铵(DAC)接枝于聚苯乙烯伯胺微球(PSA)表面,制备了接枝微粒PDAC/PSA,考察了主要因素对接枝聚合的影响,并初步探究了其对L-谷氨酸的吸附特性。结果表明,在反应温度25℃、单体质量分数为6%、引发剂占单体质量的1.2%的条件下,可制得接枝度为431mg/g的接枝微粒,其对L-谷氨酸的吸附量达140mg/g。