SURFACE MODIFICATION OF MICROPOROUS POLYPROPYLENE MEMBRANES BY GRAFT POLYMERIZATION OF N,N-DIMETHYLAMINOETHYL METHACRYLATE

Surface modification of microporous polypropylene hollow fiber membranes was performed by radical-induced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA). The influences of temperature, monomer concentration and pre-adsorbed amount of benzoyl peroxide on grafting degree were studied respectively. It was found that the appropriate graft temperature was 75 'C, at which the grafting degree was the highest and the hydrolytic decomposition of DMAEMA the lowest. Scanning electron photomicrography and the average pore diameters of the modified membranes demonstrated that part of the micropores on the membrane surface was plugged by the grafted polyDMAEMA chains, especially at high grafting degree. Contact angle and water swelling experiments showed that a moderate grafting degree could improve the hydrophilicity of the membranes. In the range of 11.3%-12.0% grafting degree, the water swelling percentage reached its maximum (51.1%) and the contact angle reached its minimum (74 degrees). The bovine serum albumin (BSA) adsorption experiment indicated that the grafted polyDMAEMA had a dual effect on protein adsorption. At the first stage, the BSA adsorption decreased with increasing of DMAEMA grafting degree. As the interaction between BSA and polyDMAEMA on membrane surface increased, the BSA adsorption increased with increasing of DMAEMA grafting degree.

PHOTO-INDUCED GRAFT POLYMERIZATION OF ACRYLAMIDE ON POLYPROPYLENE MEMBRANE SURFACE IN THE PRESENCE OF DIBENZYL TRITHIOCARBONATE

Ultraviolet （UV）-induced graft polymerization of acrylamide （AAm） on polypropylene substrates was successfully conducted using dibenzyl trithiocarbonate （DBTTC） as photoinitiator. It was confirmed by chemical analysis and surface morphology observation with attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. A possible mechanism for this graft process was presented, which suggested that, under UV irradiation, the C： S bond in DBTTC could split and abstract a hydrogen from the polypropylene surface and a surface free radical was then formed, and initiated the graft polymerization of AAm.

Ultravilolet-radiation-induced graft polymerization of acrylamide onto the melt-blown polypropylene filter element by dynamic method

By dynamic method under UV irradiation, commercial melt-blown polypropylene （PPMB） filter element was modified with acrylamide （AAm） using benzophenone （BP） as initiator. Attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscope verified that polyacrylamide chain was grafted on the fiber surface of PPMB filter element. Elemental content analysis with energy dispersive X-ray of fibers revealed that the polymerization content in the inner part of filter element was relatively higher than that in the outer. Degree of grafting changed with initiator concentration, monomer concentration, reaction temperature and reached 2.6% at the reaction condition： CBp=0.06 mol/L, CAAm=2.0 mol/L, irradiation time： 80 min, temperature： 60℃. Relative water flux altered with the hydrophilicity and pore size of filter element. In the antifouling test, the modified filter gave greater flux recovery （approximately 70%） after filtration of the water extract of Liuweidihuang, suggesting that the fouling layer was more easily reversible due to the hydrophilic nature of the modified filter.

SURFACE MODIFICATION OF POLYPROPYLENE MICROPOROUS MEMBRANE BY TETHERING POLYPEPTIDES

Two kinds of polypeptides were tethered onto the surface of polypropylene microporous membrane （PPMM） through a ring opening polymerization of L-glutamate N-carboxyanhydride initiated by amino groups which were introduced by ammonia plasma and y-aminopropyl triethanoxysilane treatments. X-ray photoelectron spectroscopy （XPS）, attenuated total reflectance Fourier transform infrared spectroscopy （FT-IR/ATR）, scanning electron microscopy （SEM）, together with water contact angle measurements were used to characterize the modified membranes. XPS analyses and FT-IR/ATR spectra demonstrated that polypeptides are actually grafted onto the membrane surface. The wettability of the membrane surface increases at first and then decreases with the increase in grafting degrees of polypeptide. Platelet adhesion and murine macrophage attachment experiments reveal an enhanced hemocompatibility for the polypeptide modified PPMMs. All these results give evidence that polypeptide grafting can simultaneously improve the hemocompatibility as well as reserve the hydrophobicity for the membrane, which will provide a potential approach to improve the performance of polypropylene hollow fiber microporous membrane used in artificial oxygenator.

UV-induced Self-initiated Graft Polymerization of Acrylamide onto Poly(ether ether ketone)

Photo-grafting of hydrophilic monomer was used to enhance the hydrophilicity of poly（ether ether ketone） （PEEK） with the aim of extending its applications to biological fields. PEEK sheets were surface modified by grafting of acrylamide（AAm） with ultraviolet（UV） irradiation in the presence or absence of benzophenone（BP）. The effects of BP, irradiation time and monomer concentration on the surface wettability of PEEK were investigated. Characteriza tion of modified PEEK using scanning electron microscopy（SEM）, energy-disperse spectrometer（EDS） and water contact angle measurements shows that AAm was successfully grafted on PEEK surface both in presence and absence of BP. With the increase in irradiation time and monomer concentration, contact angles decrease to as low as 30°, demonstrating a significant improvement of surface hydrophilicity. In agreement with the decrease in contact angle, under identical conditions, the nitrogen concentration increases, suggesting the increase in grafting degree of the grafting polymerization. This investigation demonstrates a self-initiation of PEEK due to its BP-like structure in the backbone of the polymer. Though the graft polymerization proceeds more readily in the presence of BP, the self-initiated graft polymerization is clearly observed.

Surface Modification of Nano-SiO_2 by Grafting PMMA/PBA

The surface of nano SiO 2 was modified by being encapsulated with hydroxy propyl methyl cellulose (HPMC), and then co grafted with acrylates. The grafting conditions, such as pH of the medium, and initiator concentration have been studied. The modified nano SiO 2 particles were characterized by TEM, DSC and FT IR spectra. TEM images show that the surface of the nano particles has been successfully modified by a thick layer of film like polymer in this way. The DSC results show that the decomposition temperature of modified nano particles of SiO 2 is 90 ℃ higher than that of grafted on polymer. According to the FT IR spectra, it is convinced that poly methyl methacrylate (PMMA) and poly acrylic butyl ester (PBA) were co grafted onto the surface of nano SiO 2.

Radiation induced graft polymerization of multi-walled carbon nanotubes for superhydrophobic composite membrane preparation

Highly soluble multi-walled carbon nanotubes （MWNTs） were prepared by radiation-induced free radical graft polymerization of vinyl acetate （VAc） onto pristine MWNT surfaces. High resolution transmission electron microscopy （HR-TEM）, Fourier transform infrared （FT1R） spectroscopy, and micro-Raman spectroscopy were used to confirm that poly（vinyl acetate） （PVAc） had been successfully grafted onto the surface of the MWNTs. The effects of experimental parameters on the degree of graft- ing （DG） of PVAc were also investigated, including adsorbed dose, dose rate, initial monomer concentration, and solvents. The grafted MWNTs （MWNTs-g-PVAc） exhibited good solubility in common organic solvents at high mass fraction. In addition, a superhydrophobic composite membrane could be readily fabricated by vacuum filtration of MWNTs-g-PVAc onto a support- ing membrane, as was confirmed by water contact angle testing and visualization by scanning electron microscopy.

Advances in the surface modification techniques of bone-related implants for last 10 years

At the time of implanting bone-related implants into human body,a variety of biological responses to the material surface occur with respect to surface chemistry and physical state.The commonly used biomaterials(e.g.titanium and its alloy,Co–Cr alloy,stainless steel,polyetheretherketone,ultra-high molecular weight polyethylene and various calcium phosphates)have many drawbacks such as lack of biocompatibility and improper mechanical properties.As surface modification is very promising technology to overcome such problems,a variety of surface modification techniques have been being investigated.This review paper covers recent advances in surface modification techniques of bone-related materials including physicochemical coating,radiation grafting,plasma surface engineering,ion beam processing and surface patterning techniques.The contents are organized with different types of techniques to applicable materials,and typical examples are also described.

Grafting of 2-Hydroxyethyl Methacrylate onto Silk by Atom Transfer Radical Polymerization

Silk was grafted using 2-hydroxyethyl methacrylate(HEMA)by atom transfer radical polymerization(ATRP)method.The amino groups and hydroxyl groups on the side chains of the silk fibroin was reacted with 2-bromoisobutyryl bromide(BriB-Br)to obtain efficient macroinitiator for ATRP.And the macroinitiator was grafted with HEMA in water aqueous using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine(PMDETA)as catalyst system.The effects of monomer concentration,the proportion of CuBr and PMDETA,grafting temperature and time on the silk grafting were discussed,and the optimal grafting technology was obtained.FT-IR characterization of the grafted silk showed a peak corresponding to HEMA,which indicated that HEMA was grafted onto the surface of silk.ATRP method could be applied on the silk modification and this technique provided a new way for silk grafting.

PLASMA MODIFICATION OF POLYPROPYLENE SURFACES AND GRAFTING COPOLYMERIZATION OF STYRENE ONTO POLYPROPYLENE

The surface of polypropylene （iPP） is modified with glow discharge plasma of Ar, so that the modified surfaces of iPP films are obtained. The studies of scanning electron microscopy （SEM） show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy （XPS） and Fourier transform infrared （FTIR） spectroscopy. The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated. The free radical of modification surfaces of iPP is measured by chemical method. The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene （St） in St. The grafting polymer of St onto iPP is characterized by FTIR. The grafting rate is dependent on plasma exposure time and discharge voltage. The studies show that homopolymerization of St is undergone at the sane time during the graftingcopolymerization of St onto/PP.

Performances of biological aerated filter employing hollow fiber membrane segments of surface-improved poly(sulfone) as biofilm carriers

Using the surface of poly （sulfone） hollow fiber membrane segments as grafted layer, the hydrophilic acrylamide chain was grafted on by UV-photoinduced grafting polymerization. The gained improvement of surface wettability for the modified membrane was tested by measuring the contact-angle as well as FTIR spectra. Then correlation between the hydrophilic ability of support material and the biofilm adherence ability was demonstrated by comparing the pollutant removal rates from urban wastewater via two identical lab-scale up-flow biological aerated filters, one employed the surface wettability modified poly （sulfone） hollow fiber membrane segment as biofilm carder and the other employed unmodified membrane segment as biofilm carder. The experimental results showed that under the conditions of influent flux 5 L/h, hydraulic retention time 9 h and gas to liquid ratio （G/L） 10： 1, the removal rates of chemical oxygen demand （COD） and ammonium nitrogen （NH4^＋-N） for the modified packing filter and the unmodified packing filter was averaged at 83.64% and 96.25%, respectively, with the former filter being 5%-20% more than the latter. The effluent concentration of COD, NH4^＋-N and turbidity for the modified packing filter was 25.25 mg/L, 2 mg/L and 8 NTU, respectively. Moreover, the ammonium nitrogen removal performance of the filter packing the modified PSF was compared with the other bioreactor packing of an efficient floating medium. The biomass test indicated that the modified membrane matrixes provided better specific adhesion （3310-5653 mg TSS/L support）, which gave a mean of 1000 mg TSS/L more than the unmodified membrane did. In addition, the phenomenon of simultaneous denitrification on the inner surface of the support and nitrification on the outer surface was found in this work.

Plasma Induced Grafting of PMMA onto Titanium Dioxide Powder

Grafting of polymer of methyl methacrylate （PMMA） onto titanium dioxide powder is investigated in this paper. The graft polymerization reaction is induced by dielectric-barrier- discharge produced N2 plasma treatment of titanium dioxide surfaces. IR, XPS and TGA results show that PMMA is grafted onto the surfaces of titanium dioxide powder. And crystal structure of the titanium dioxide powder observed with XRD spectra is unchanged after plasma graft polymerization.

High Frequency Discharge Plasma Induced Grafting of Polystyrene onto Titanium Dioxide Powder

Grafting of polystyrene （PS） onto titanium dioxide powder was investigated. The graft polymerization reaction was induced by high frequency discharge produced N2 plasma treatment of the surfaces of titanium dioxide. IR, XPS and TGA results show that PS was grafted on the titanium dioxide powder. And the crystal structure of the titanium dioxide powder observed by XRD was unchanged after plasma treatment.

Preparation of polystyrene/SiO_(2) nanocomposites by surface-initiated nitroxide-mediated radical polymerization

Polystyrene/SiO2 composite nanoparti- cles (PS-g-Silica) were prepared by an in-situ sur- face-initiated nitroxide-mediated radical polymeriza- tion. After SiO2 nanoparticles were treated by thionyl chloride (SOCl2), peroxide initiation groups were immobilized on their surfaces through a reaction with tertiary butyl hydroperoxide (TBHP). Then surface nitroxide-mediated radical polymerization was initi- ated and polystyrene was grafted on the surface of SiO2 particles. Composite nanoparticles were char- acterized by IR spectra, transmission electron mi- croscopy (TEM), atomic force microscopy (AFM) and thermogravimetry (TGA) and the results indicated that the surface-initiated nitroxide-mediated radical polymerization could be successfully used to synthe- size well-dispersive PS/SiO2 nanocomposites.

表面接枝TAPI改善聚酰胺纳滤膜的耐氯性能

为了改善聚酰胺纳滤膜的耐氯性,通过表面改性将2,4,6-三氨基嘧啶(TAPI)接枝到聚酰胺膜表面,利用ATR-FTIR、SEM和接触角测定仪等手段对改性膜进行表征.结果表明,在TAPI最优质量分数为0.3%,最佳反应时间为3 min时,改性膜在0.4 MPa操作压力下,纯水通量为43.52 L/(m^(2)·h),对Na_(2)SO_(4)、MgSO_(4)、NaCl和MgCl_(2)的截留率分别为95.30%、88.04%、45.32%、34.04%.pH=3.5、7、10.5下的氯化实验中,改性膜的通量损失量均比哌嗪基纳滤膜减少20 L/(m^(2)·h),并且对Na_(2)SO_(4)截留率保持稳定在95%以上.

聚乙烯的表面光接枝改性研究进展

综述了紫外光引发接枝改性聚乙烯表面的研究进展 ,包括光接枝聚合机理、改性方法、接枝链的结构和形态。

UV改性DACRON材料抗细菌粘附研究

介绍了对人工心瓣植入用涤纶布 (Dacron)表面以紫外辐照为主进行接枝改性的方法 ,在其材料表面引入聚乙二醇 (Polyethlene glycol,PEG) ,利用 PEG的“化学放大”作用再引入肝素 (Heparin,Hep) ,改性后的材料抗细菌粘附效果显著 ,与未改性材料相比 ,细菌粘附减少 90 %。

纳米SiO_2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%.

亲水膜的表面改性及在膜蒸馏中的应用

膜的微孔性和疏水性是水溶液膜蒸馏的两个基本条件,迄今人们均采用疏水性高分子材料制成疏水微孔膜用于膜蒸馏研究。本文采用辐照接枝聚合和等离子体表面聚合的方法,将亲水的醋酸纤维素微孔膜和硝酸纤维素微孔膜表面疏水化改性,成功地用于膜蒸馏研究,大大扩展了疏水微孔膜的材料来源。实验结果表明,亲水膜表面改性得到的疏水膜,其膜蒸馏性能不低于疏水材料制成的膜,尤其是等离子体聚合法可以实现多种特殊单体在多孔的材料表面聚合,成为制备高性能疏水微孔膜的有效手段,为膜蒸馏的深入发展和实用化创造了有利条件。

纳米SiO_2表面上的聚对苯二甲酸丁二醇酯预聚物接枝改性

在纳米SiO2表面上进行聚对苯二甲酸丁二醇酯预聚物(pre-PBT)接枝改性,建立空间位阻稳定层, 提高了纳米SiO2的分散稳定性,增强了纳米粒子与树脂基体的相容性。红外光谱表明,接枝纳米粒子存在着 pre-PBT的酯基特征吸收峰,XPS的Si2p峰精细扫描表明二者形成了Si-O-C键,结合能降低;缩合聚合接枝体系的反应压力是影响纳米SiO2表面接枝量和接枝链长的重要因素,热失重分析和粘均分子量测定表明,随着反应压力的降低,热失重增加,接枝物分子量升高,接枝链变长;AFM观察表明在四氯乙烷中分散后的粒径约为50nm,几乎所有颗粒都以原生粒子的状态单独分散,颗粒间无团聚。SEN分析表明,接枝纳米粒子在聚对苯二甲酸丁二醇酯(PBT)树脂基体中可均匀地分散,二者界面间存在较强的界面作用。