Grafting of glycidyl methacrylate onto polypropylene using supercritical carbon dioxide

Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studied using supercritical carbon dioxide (SC-CO₂) as a solvent and a swelling agent. As the reaction temperature was below the melting point, PP was modified in the solid phase. The PP film was first soaked with the monomer GMA and benzoyl peroxide (BPO) as an initiator using SC-CO₂ at different experimental conditions of pressure, temperature, and thermal treatment time. After releasing CO₂, film GMA molecules were grafted onto PP in different times. Using this method, the degree of grafting and the morphology could be controlled through the combination of pressure, temperature, and soaking time. FTIR spectra confirmed that GMA had been grafted onto PP and that polypropylene-graft-glycidyl methacrylate (PP-g-GMA) presented a high surface reactivity for conductive polyaniline anchoring. DSC measurements and TG analyses showed that the thermal profiles of the graft copolymer and virgin PP are quite similar and that the graft PP does not exhibit changes in terms of thermal degradation profile and melting temperature, respectively. X-ray data showed that a high degree of grafting leads to a lower degree of crystallinity of polypropylene.     

聚乙烯表面接枝聚合改性及抗凝血性的研究

聚乙烯(PE)膜经Ar等离子体预处理,无光引发剂紫外光照接枝甲基丙烯酸缩水甘油酯(GMA),然后进行肝素化处理,以改善PE的抗凝血性能。用正交实验确定接枝反应的最优条件。通过X-射线光电子能谱(XPS)、衰减全反射红外光谱(ATR-FTIR)、扫描电子显微镜(SEM)和接触角测定PE膜接枝GMA前后表面性能和表面形貌。用复钙时间、凝血酶原时间、部分凝血活酶时间、凝血酶时间和血小板粘附实验对其抗凝血性能进行评价,结果表明,被修饰PE膜的抗凝血性能显著提高。     

Effect of supercritical CO2 in modified polystyrene 3D latex arrays

The effect of supercritical CO(2) (scCO(2)) in 3D latex arrays formed by monodispersed particles of polystyrene (PS), PS cross-linked with divinylbenzene (PS-DVB), and PS block copolymers with 2-hydroxyethyl methacrylate (PS-HEMA), methacrylic acid (PS-MA), acrylic acid (PS-AA), itaconic acid (PS-IA), and a mixture of methacrylic and itaconic acid (PS-IA-MA) has been studied. Sorption of CO(2) into the polymer particles leads to a decrease in the glass transition temperature of the polymer and the swelling of the particles and induces their coalescence. 3D-latex arrays of the former compositions were treated in scCO(2) at temperatures and pressures ranging from 40 to 80 degrees C and from 85 to 197 bar, respectively. The effect of CO(2) on the polymeric template was assessed by scanning electron microscopy and N(2) adsorption analysis. Bare PS and PS-HEMA particles sintered readily in scCO(2) at 40 degrees C and 85 bar. On the other hand, particles containing carboxylic acid groups on their surface (PS-MA, PS-AA, PS-IA, and PS-IA-MA) were, at the same temperature and pressure, more resistant to the CO(2) treatment. For a given polymer composition, the sorption of CO(2) inside the polymer particles, the swelling, and the degree of coalescence depend on the pressure, temperature, and time of the CO(2) treatment. Analysis of the pore size distributions from the N(2) adsorption data has allowed us to quantify the degree of coalescence of the particles in the matrix. By careful control of the experimental variables, the coalescence of the 3D latex array could be finely tuned using CO(2).     

Plasma polymerization and deposition of glycidyl methacrylate on Si(100) surface for adhesion improvement with polyimide

Thin polymer films were deposited on Si(100) surfaces by plasma polymerization of glycidyl methacrylate (GMA) under different glow discharge conditions. The FT‐IR, X‐ray photoelectron spectroscopy (XPS), and amine treatment results suggested that the epoxide functional groups of the deposited films had been preserved to various extents, depending on the plasma deposition conditions. The use of a low radio frequency power (～ 5 W) and a relatively high system pressure (100–400 Pa) readily resulted in the deposition of thin films having nearly the same composition of the epoxide functional groups as that of the GMA homopolymer. The plasma‐polymerized GMA (PP‐GMA) thin films deposited on the Ar plasma‐pretreated Si(100) surfaces were retained to a large extent after acetone extraction, suggesting the presence of covalent bonding between the PP‐GMA layer and the Si surface. Thermal imidization of the poly(amic acid) precursor of polyimide on the GMA plasma‐polymerized Si(100) surface resulted in a strongly adhered polyimide film. The adhesion results further suggested that the GMA polymer had been grafted on the Si(100) surface and the epoxide functional groups had undergone reactive interaction (curing) with the carboxylic and amine groups of the poly(amic acid) during thermal imidization. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermo-mechanical and electro-optical properties of polymer dispersed liquid crystal films

We have observed a strong dependence of the electro-optical properties of polymer dispersed liquid crystal (PDLC) films on temperature. One plausible explanation for this dependence is the thermal expansion of the films. We investigated the thermal expansion of various PDLC films using a thermal mechanical analyser (TMA). As the temperature increased, the films expanded and their droplet size decreased, and their contrast, response time, and hysteresis changed simultaneously. We observed obvious changes of thermal expansion coefficient of the films. We studied the qualitative relationship between thermo-mechanical properties and electrooptical properties. The thermal expansion of PDLC films could be adjusted by changing the degree of cross-linking of the polymer.     

甲基丙烯酸缩水甘油酯/苯乙烯固相接枝聚丙烯

以苯乙烯(St)为共单体，过氧化苯甲酰(BPO)为引发剂，采用固相接枝反应将甲基丙烯酸缩水甘油酯(GMA)接枝到聚丙烯(PP)大分子链上。研究了反应时间、单体用量、引发剂用量等因素对接枝率的影响。采用凝胶渗透色谱(GPE)测定了PP和接枝物PP-g-(GMA-St)的分子量和分子量分布。结果 表明固相接枝PP反应条件为[GMA／[St]=2，反应3．5h，加入GMA 10份，BPO 5份。St的加入有助于GMA与PP的接枝，同时在一定程度上抑制了PP的降解。     

棉纤维的N-异丙基丙烯酰胺接枝共聚及产物的温敏性研究

以硝酸铈铵(CAN)、过硫酸钾(KPS)及H2O2/H2A(双氧水/抗坏血酸)为引发体系,采用溶液自由基接枝法制备了具有温敏性的棉纤维N-异丙基丙烯酰胺接枝共聚物(cotton-g-PNIPAAm);在上述3种引发剂作用下的接枝反应可以达到的接枝率(G)排序为G(H2O2/H2A)>G(KPS)>G(CAN);研究了其他因素如引发剂浓度、反应时间、反应温度和单体浓度等对接枝率的影响,得出了优化的接枝反应条件;接枝样品的FTIR分析图谱和SEM观察均表明样品表面已接枝了聚N-异丙基丙烯酰胺;DSC分析显示,棉纤维N-异丙基丙烯酰胺接枝共聚物的低临界溶解温度(LCST)与纯的聚N-异丙基丙烯酰胺凝胶(LCST=32.48℃)相似,约为32~33℃;接枝率的变化对试样LCST的影响很小,但其可逆焓变(ΔH)会随接枝率的提高而增加;采用滴水试验法(AATCC 79)和毛效试验法(FZ/T 01071)检测棉纤维的N-异丙基丙烯酰胺接枝共聚物在不同温度时的吸水性变化,显示试样具有温敏特性,其中接枝率介于25%~45%的试样温敏性较高,过低或过高的接枝率均不利于获得高的温敏性;棉纤维的N-异丙基丙烯酰胺接枝共聚物试样的可逆焓变(ΔH)随试样膨胀/收缩时间变化的研究和分析结果表明,棉纤维的N-异丙基丙烯酰胺接枝共聚物对温度变化的响应比纯聚N-异丙基丙烯酰胺凝胶快.     

Preparation and characterization of a novel thermally stable unsaturated poly(ester-imide) based on 1,4-bis[2′-trifluoromethyl-4′-(4″-carboxylic acid)trimellitimido phenoxy]benzene

A novel thermally stable unsaturated poly(ester-imide) (UPEI-50) was prepared by thermal polycondensation of a diimidodicarboxylic acid monomer, 1,4-bis[2′-trifluoromethyl-4′-(4″-carboxylic acid)trimellitimido phenoxy]benzene (BTTB), maleic anhydride and 1,2-propylene glycol. The poly(ester-imide) resin obtained was found to be easily dissolved in glycidyl methacrylate (GMA) to give a homogeneous resin composition with low viscosity, which was then thermally cured into thermosetting poly(ester-imide)/glycidyl polymethacrylate polymer composite (UPEI-50/GMA). Effects of curing processing parameters such as the curing temperature and curing time, the reactive monomer concentration and the initiator amount etc. on curing reaction were systematically investigated. Experimental results indicated that the thermally cured UPEI-50/GMA polymer composite exhibited outstanding thermal stability, mechanical and electrical insulating properties.     

共溶剂对超临界CO2注入技术制备聚丙烯/SiO2纳米复合材料的影响

采用超临界CO2注入技术制备聚合物-无机纳米粒子复合材料, 以乙醇作为共溶剂, 在超临界CO2中将正硅酸乙酯(TEOS)注入到聚丙烯(PP)中, 重点研究共溶剂乙醇对TEOS在PP中注入率的影响. 实验结果表明注入率随着共溶剂加入先增加后减小. 同时研究了在共溶剂的存在下其他实验条件对注入率的影响. 并采用卢瑟福背散射能谱法(RBS)分析了聚丙烯/SiO2纳米复合材料的注入元素深度分布, 发现Si元素在PP中的浓度分布不均匀, 随着深度的增加而减小.     

Reactive processing of polymers: Effect of bifunctional and tri-functional comonomers on melt grafting of glycidyl methacrylate onto polypropylene

Two reactive comonomers, divinyl benzene (DVB) and trimethylolpropane triacrylate (TRIS), were evaluated for their role in effecting the melt free radical grafting reaction of the monomer glycidyl methacrylate (GMA) onto polypropylene (PP). The characteristics of the GMA-grafting systems in the presence and absence of DVB or TRIS were examined and compared in terms of the yield of the grafting reaction and the extent of the main side reactions, namely homopolymerisation of GMA (poly-GMA) and polymer degradation, using different chemical compositions of the reactive systems and processing conditions. In the absence of the comonomers, i.e. in a conventional system, high initiator concentrations of peroxides were typically required to achieve the highest possible GMA grafting levels which were found to be generally low. Concomitantly, both poly-GMA and degradation of the polymer by chain scission takes place with increasing initiator amounts. On the other hand, the presence of a small amount of the comonomers, DVB or Tris, in the GMA-grafting system, was shown to bring about a significant increase in the grafting level paralleled by a large reduction in poly-GMA and PP degradation. In the presence of these highly reactive comonomers, the optimum grafting system requires a much lower concentration of the peroxide initiator and, consequently, would lead to the much lower degree of polymer degradation observed in these systems. The differences in the effects of the presence of DVB and that of TRIS in the grafting systems on the rate of the GMA-grafting and homopolymerisation reactions, and the extent of PP degradation (through melt flow changes), were compared and contrasted with a conventional GMA-grafting system.     

原子转移自由基聚合法制备新型亲水开管毛细管柱及在毛细管电色谱上的应用

为了增加开管毛细管柱(OTCC)的相比,提高分离效率,发展了表面引发原子转移自由基聚合法(SI-ATRP)制备葡萄糖聚合物修饰的开管毛细管柱。通过扫描电镜观察,该开管柱内壁上修饰了三维波浪状聚合物,明显增加了内壁比表面积和相比。在pH 3~11范围内,对含糖聚合物修饰的开管柱和空柱的电渗流进行了比较。修饰后开管柱的电渗流仅为空柱的1/2~1/3,且在pH 6~11范围内保持平稳。稳定的电渗流保证了分离的重复性和稳定性。用该开管毛细管柱成功实现了小分子混合物(苯丙氨酸、胸腺嘧啶、腺苷、鸟苷、5-溴尿嘧啶、水杨酸)以及蛋白质大分子(核糖核酸酶B、转铁蛋白和牛血清白蛋白)的有效分离,结果表明葡萄糖聚合物修饰的开管毛细管柱具有良好的重复性和稳定性。     

Graft copolymerization of maleic anhydride/styrene onto isotactic polypropylene using supercritical CO2

The free‐radical grafting of maleic anhydride (MAH) and styrene (St) onto isotactic polypropylene (iPP) was studied by thermal decomposition of dicumyl peroxide (DCP) using supercritical CO₂ as a solvent and swelling agent. Several effects of molar ratio of monomer, soaking temperature and time, reaction time, and reaction pressure on the graft degree were discussed. It was found that the addition of St to the grafting system as a comonomer could significantly enhance the graft degree of the grafted PP. Under the optimal reaction condition, the maximum of iPP grafting MAH and St in supercritical CO₂ medium was 10.58%. The chemical structures and properties of grafting copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The results showed that the supercritical CO₂ method had noticeable advantages over the existed method when compared, such as a lower temperature, a higher graft degree, easy separation, and environmentally benign. Copyright © 2007 John Wiley & Sons, Ltd.     

Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement

After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008     

Graft Copolymerization of 2-Hydroxy Ethyl Methacrylate onto Chitosan with Cerium (IV) Ion. I. Synthesis and Characterization

Graft copolymerization of 2-Hydroxy ethyl methacrylate (HEMA) on to chitosan was studied using cerium (IV) as the initiator. Optimization of the grafting was worked out by varying the reaction time and monomer concentration. Under controlled conditions, up to 685% grafting with a grafting yield of 92.4% was achieved. FTIR, thermal and XRD techniques were used to confirm the formation of the grafted copolymer. Grafting caused a marginal decrease in the mechanical strength in the dry conditions and a significant decrease under wet conditions for the resultant polymer. The products showed significantly improved swelling at pH 7.4 and pH 1.98 compared to the original chitosan. Grafted polymer showed enhanced Tg and decomposition temperature. The grafting also resulted in improved hydrophilicity as is evident from the contact angle studies of the films.     

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions,and its application to metal adsorbent

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0 mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50 kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0 mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA–grafted NWPE (GMA–g-NWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA–g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000 h^?1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16 mmol-Pb(II)/g-adsorbent.     

WATER-SOLUBLE AMPHOLYTIC GRAFTED POLYSACCHARIDES. 1. GRAFTING OF THE ZWITTERIONIC MONOMER 2-(2-METHACRYLO-ETHYLDIMETHYLAMMONIO) ETHANOATE ONTO HYDROXYETHYL CELLULOSE

Novel ampholytic grafted polysaccharides were prepared by grafting the Zwitterionic monomer 2-(2-methacryloethyldimeth-ylammonio) ethanoate onto hydroxyethyl cellulose. Ethylenediamine tetraacetic acid was used in combination with ceric ammonium nitrate as the redox initiator. The effects of various factors such as initiator amount, monomer concentration, reaction temperature and time on the grafting were studied and the optimum reaction conditions to obtain maximum degree of grafting were found. The resulted graft copolymer was characterized by IR and thermal analyses.     

Radiation-induced grafting of perfluorinated vinyl ether into fluorinated polymer films

We report herein the first successful grafting of perfluorinated vinyl ether monomer into base polymer films by simultaneous radiation method. 2-Bromotetrafluoroethyl trifluorovinyl ether (BrTFF) could be grafted into poly(ethylene-co-tetrafluoroethylene) (ETFE) films by γ-rays irradiation at room temperature. The grafting yield increased linearly with an increase in the dose up to 1400 kGy. The required dose for a satisfactory grafting yield, such as 20%, was as high as ca. 400 kGy probably due to low polymerization reactivity of fluorinated monomers. However, the solvent and catalyst had no positive influence for improving the grafting yield. FTIR spectra and SEM-EDS testified that BrTFF was successfully grafted into ETFE films homogeneously in the perpendicular direction. The thermal analysis of the grafted films further indicated no phase separation between poly(BrTFF) grafts and ETFE films, probably owing to high compatibility of the fluorinated grafts and base polymers.     

Pre-irradiation induced grafting of styrene into crosslinked and non-crosslinked polytetrafluoroethylene films for polymer electrolyte fuel cell applications. I: Influence of styrene grafting conditions

Crosslinked and non-crosslinked polytetrafluoroethylene (PTFE) films [RX-PTFE and V-PTFE films, respectively], were irradiated in air at room temperature using γ-rays from a ⁶⁰Co source. The irradiated films were grafted with styrene in liquid phase. The grafting of styrene into PTFE films was proved by FT-IR spectroscopy. The influence of the reaction temperature and pre-irradiation doses on the resulted degree of grafting was discussed. The grafting speed and the degree of grafting were determined by the reaction temperature and pre-irradiation doses. The apparent activation energies were calculated as 39.7 kJ/mol for RX-PTFE films and 59.5 kJ/mol for V-PTFE films. The dependence index on absorbed doses at pre-irradiation for RX-PTFE films is 0.66, and for V-PTFE films it is 1.57. The geometric size changes of the grafted films were measured and discussed. Interestingly, the thickness of the grafted films was strongly influenced by the reaction temperature. The tensile strength and the elongation at break of the non-grafted and grafted RX-PTFE and V-PTFE films were measured. The grafted films then are sulfonated by chlorosulfonic acid for polymer electrolyte fuel cell (PEFC) applications and the highest IEC value gained is over 3. The analysis of the sulfonated films are now in progress.     

Controlled grafting of well-defined epoxide polymers on hydrogen-terminated silicon substrates by surface-initiated ATRP at ambient temperature

Controlled grafting of well-defined epoxide polymer brushes on the hydrogen-terminated Si(100) substrates (Si-H substrates) was carried out via the surface-initiated atom-transfer radical polymerization (ATRP) at room temperature. Thus, glycidyl methacrylate (GMA) polymer brushes were prepared by ATRP from the alpha-bromoester functionalized Si-H surface. Kinetic studies revealed a linear increase in GMA polymer (PGMA) film thickness with reaction time, indicating that chain growth from the surface was a controlled "living" process. The graft polymerization proceeded more rapidly in the dimethylformamide/water (DMF/H(2)O) mixed solvent medium than in DMF, leading to much thicker PGMA growth on the silicon surface in the former medium. The chemical composition of the GMA graft-polymerized silicon (Si-g-PGMA) surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The fact that the epoxide functional groups of the grafted PGMA were preserved quantitatively was revealed in the reaction with ethylenediamine. The "living" character of the PGMA chain end was further ascertained by the subsequent growth of a poly(pentafluorostyrene) (PFS) block from the Si-g-PGMA surface, using the PGMA brushes as the macroinitiators.     

DLVO-based estimates of adsorbed water film thicknesses in geologic CO2 reservoirs

When supercritical carbon dioxide (scCO(2)) is injected into deep subsurface reservoirs, much of the affected volume consists of pores containing both water and scCO(2), with water films remaining as the mineral-wetting phase. Although water films can affect multiphase flow and mediate reactions at mineral surfaces, little is known about how film thicknesses depend on system properties. Here, the thicknesses of water films were estimated on the basis of considerations of capillary pressure needed for the entry of CO(2) and disjoining pressures in films resulting from van der Waals and electric double-layer interactions. Depth-dependent CO(2) and water properties were used to estimate Hamaker constants for water films on silica and smectite surfaces under CO(2) confinement. Dispersion interactions were combined with approximate solutions to the electric double layer film thickness-pressure relationship in a Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis, with CO(2) as the confining fluid. Under conditions of elevated pressure, temperature, and salinity commonly associated with CO(2) sequestration, adsorbed water films in reservoir rock surfaces are typically predicted to be less than 10 nm in thickness. Decreased surface charge of silica under the acidic pH of CO(2)-equilibrated water and elevated salinity is predicted to compress the electric double layer substantially, such that the dispersion contribution to the film thickness is dominant. Relative to silica, smectite surfaces are predicted to support thicker water films under CO(2) confinement because of greater electrostatic and dispersion stabilization.