Radiation-induced grafting polymerization by the ionic mechanism

A technique of radiation-induced grafting under conditions of extreme drying of monomers has been developed. Under such conditions, radiation-induced grafting polymerization of isobutylene, -methylstyrene, vinyl-n-butyl ether, styrene, acrylonitrile, and 4-vinylpyridine by the ionic mechanism at room temperature has been performed. The grafted copolymers of polyethylene, Teflon and polyvinyl chloride with monomers polymerized only ionically (isobutylene, -methylstyrene, vinyl-n-butyl ether) have been obtained for the first time. The kinetics of the radiation-induced grafting of vinyl-n-butyl ether on to polyethylene have been studied; the ionic mechanism has been confirmed. It has been found that the rates of the radiation-induced ionic grafting of styrene, acrylonitrile, and 4-vinylpyridine are much greater than those for radical grafting. The highest grafting rates are observed for 4-vinylpyridine. The mechanism of radiation-induced ionic grafting polymerization has been discussed; generalized kinetic equations have been derived to account for the contributions from radical and ionic processes.     

Free radical polymerization of glycidyl methacrylate in plasticized Poly(vinyl chloride)

Kinetic of free radical in-situ polymerization of glycidyl methacrylate (GMA), was studied in a complex evolutionary system: poly(vinyl chloride) (PVC) plastisols. A predictive model of conversion-time profile based on free radical mechanism was proposed and structure of the modified PVC system developed was investigated by NMR analyses. In order to elucidate the mechanism of the reaction, model molecules for PVC were used with NMR and MALDI-TOF characterization. It was found that in-situ polymerization of GMA in PVC plastisols leads to both homopolymerization and grafting of GMA onto PVC backbone by hydrogen abstraction. For 33 wt% GMA loaded, grafting efficiency is 67% with an amount of grafted poly-glycidyl methacrylate (pGMA) equals to 22 wt%. Thus, this article discloses a new type of PVC plastisols called reactive plastisols where, in addition to usual plasticizers, PVC is modified by polymerizable GMA monomer.     

Physicomechanical properties of grafted polymers obtained by radiation-induced polymerization by radical and ionic mechanisms

The radiation-induced grafting of acrylonitrile, 4-vinylpyridine, and styrene was carried out by both radical and ionic mechanisms. Grafted polymers with equal percentages of graft were obtained by the radical and ionic propagation of the grafted chains. The molecular weight of homopolymers has been determined. The thermomechanical properties of the graft polymers were investigated. The yield temperatures for the graft polymers obtained by ionic propagation of the grafted chains is higher than that of graft polymers obtained by a radical mechanism. This is attributed to the higher molecular weight of the grafted chains obtained by the radiation-induced grafting by the ionic mechanism. The radiation-induced grafting of polyacrylonitrile increases significantly the thermal stability of polyethylene. The differential thermal analysis shows no marked differences in properties of the polymers.     

Effect of sovents on radiation-induced ionic graft polymerization

The influence of various solvents on radiation-induced cationic (grafting of vinyl-n-butyl ether onto polyethylene) and anionic (grafting of 2-methyl-5-vinylpyridine onto polyethylene) graft polymerization was studied. This ionic grafting was performed in thoroughly dried systems at room temperature. It was established that electron-acceptor solvents promote cationic grafting but that electron-donor solvents promote the anionic. A clear correlation between the donor number of solvents and grafting value by the anionic mechanism was shown. There was no correlation between dielectric constants and grafting values. The reaction orders, according to monomer concentration by 2-methyl-5-vinylpyridine grafting in various solvents, were equal to approximately 1.5 and 2 for the radical and anionic mechanisms, respectively. The effect of solvents on radiation-induced ionic graft polymerization is discussed. The results of this study indicate the correct choice of solvents for radiation-induced ionic grafting.     

Grafting of polymers onto and/or from silica surface during the polymerization of vinyl monomers in the presence of γ‐ray‐irradiated silica

The effects of radicals on silica surface, which were formed by γ‐ray irradiation, on the polymerization of vinyl monomers were investigated. It was found that the polymerization of styrene was remarkably retarded in the presence of γ‐ray‐irradiated silica above 60 °C, at which thermal polymerization of styrene is readily initiated. During the polymerization, a part of polystyrene formed was grafted onto the silica surface but percentage of grafting was very small. On the other hand, no retardation of the polymerization of styrene was observed in the presence of γ‐ray‐irradiated silica below 50 °C; the polymerization tends to accelerate and polystyrene was grafted onto the silica surface. Poly(vinyl acetate) and poly(methyl methacrylate) (MMA) were also grafted onto the surface during the polymerization in the presence of γ‐ray‐irradiated silica. The grafting of polymers onto the silica surface was confirmed by thermal decomposition GC‐MS. It was considered that at lower temperature, the grafting based on the propagation of polystyrene from surface radical (“grafting from” mechanism) preferentially proceeded. On the contrary, at higher temperature, the coupling reaction of propagating polymer radicals with surface radicals (“grafting onto” mechanism) proceeded to give relatively higher molecular weight polymer‐grafted silica. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2972–2979, 2006     

铈盐引发聚醚氨酯膜上丙烯酰胺接枝聚合反应

由聚四亚甲基醚二醇、4,4′-二苯基甲烷二异氰酸酯与乙二胺或丁二醇扩链剂合成的聚醚氨酯薄膜,可顺利地在室温下用硝酸铈铵引发接枝丙烯酰胺共聚合反应,这可以从反应后的薄膜由起始时是透明的而变为不透明,也可以从接枝后的薄膜比基膜有较大的吸水率,以及从扫描电子显微镜观察到薄膜表面上有凸起图象的高分子链所证实,由于先发生接枝共聚合而后才是均聚反应,因而保证了接枝后的薄膜几乎不附着聚丙烯酰胺。     

Improving the hydrophilic and antifouling properties of poly(vinyl chloride) membranes by atom transfer radical polymerization grafting of poly(ionic liquid) brushes

In this study, poly(1‐butyl‐3‐vinylimidazolium bromide) (PBVIm‐Br) was grafted onto the poly(vinyl chloride) (PVC) membrane surface via a 2‐step atom transfer radical polymerization (ATRP) reaction. Poly(2‐hydroxyethylmethacrylate) (PHEMA) was grafted onto the membrane surface by aqueous ATRP reaction; then, BVIm‐Br was introduced onto the surface of the PHEMA‐modified PVC membrane through traditional ATRP reaction. The analysis of surface chemistry confirmed the successful grafting of PHEMA and PBVIm‐Br on PVC membrane surface, and the grafting density (GD) of PBVIm‐Br gradually increased as the grafting time was prolonged. The modified membrane exhibited a positive charge and significantly enhanced surface hydrophilicity. The static water contact angle of the membrane surface decreased from 92.3° to 51.6° as the GD of the PBVIm‐Br brushes increased. Filtration experiments indicated that the water flux of the modified membrane increased with increasing GD, and their recovered fluxes were more than twice than the original. In addition, the total fouling ratio of the membranes decreased from 89% in M0 to 67% in M5, and most of the fouling was reversible as the GD of PBVIm‐Br brushes increased. These results indicated that the positive charged poly(ionic liquid) brushes featuring hydrophilic properties would have potential applications in membrane separation.     

Graft Copolymerization of Benzyl Methacrylate onto Poly(Acryloyl-L-valine) Microspheres by Using the Photoreaction of Side Carboxyl Groups with Lead Tetraacetate

N-Acryloyl-L-valine (ALV) was found to yield polymer microspheres when it was polymerized with a radical initiator in acetophenone. The resulting microspheres showed thermochromism in aromatic solvents such as benzonitrile, methyl benzoate, and acetophenone. Graft copolymerization of benzyl methacrylate (BzMA) onto poly(ALV) microspheres was carried out in benzonitrile by using the photoreaction of carboxyl groups in poly (ALV) with Pb(OAc)₄. The grafting efficiency was not very high (15–28%). Methyl methacrylate as the second monomer gave a higher grafting efficiency (56%) although the polymer yield was considerably lower. The resulting graft copolymer was characterized by IR spectroscopy and thermogravimetry. The grafted poly (ALV) microspheres were well dispersed in benzene. A benzene solution of grafted poly(ALV) microspheres and homopoly(BzMA) gave a film with finely dispersed poly (ALV) microspheres.     

Radiation-induced grafting polymerization by the anionic mechanism

The radiation-induced grafting polymerization of phenylacetylene and 2-methyl-5-vinylpyridine (2M-5VPy) onto low-density polyethylene has been investigated under strict identical conditions, using crude and thoroughly dried monomers. In the case of thoroughly dried monomers, the radiation-induced grafting is performed by the combined (radical + anionic) mechanism. The kinetics of radical and anionic grafting of 2M-5VPy are investigated in detail. The activation energies are 4.8 ± 0.3 and ?2.7 ± 0.3 kcal/mole for the radical and anionic grafting, respectively. The initial rate of grafting is approximately proportional to the dose rate to the 0.47 ± 0.03 and 0.92 ± 0.03 power for the radical and anionic grafting, respectively. The initial rate of grafting is approximately proportional to monomer concentration to the 1.55 ± 0.05 and 2.1 ± 0.05 power for the radical and anionic grafting, respectively. These data conform to the contribution of the anionic mechanism in a thoroughly dried system. The mechanism of radiation-induced anionic grafting is discussed.     

辐射接枝法制备离子交换膜的研究现状

聚合物离子交换膜有多种制备方法，其中高分子材料辐射引发接枝功能性单体是一种文献中屡见报道且简单可行的方法．通过在不同聚合物基体上接枝各种类型的单体，可以改变接枝膜的电化学性能、物理化学等性能．丈中详细介绍了不同的高分子基材辐射接枝各类单体制备聚合物离子交换膜的研究现状．     

Radiation-induced grafting in the polyethylene–styrene system and differential thermal analysis of the grafted samples

The graft polymerization of styrene onto high-density polyethylene films was carried out by γ-irradiation in the vapor phase. Two methods were used for grafting in these experiments: a preirradiation method and a simultaneous irradiation method. The effects of these grafting methods on the reaction mechanism of grafting and on the properties of the grafted samples were investigated. The amounts of styrene homopolymer in the grafted samples is under 2% in the case of the preirradiation method and above 10% in the case of the simultaneous irradiation method. The activation energies were calculated to be 18 kcal/mole for grafting in the preirradiation method and 15 kcal/mole for weight increase of polyethylene films in styrene vapor. The difference in the dimensional expansion between in the direction of stretching and the direction prependicular to it is smaller with preirradiation grafting than with grafting by the simultaneous irradiation method. Differential thermal analysis of the grafted films shows an endothermic peak due thermal decomposition which decreases gradually from 450°C to 415°C with increase in degree of grafting from 30 to 60%. The lowering of this peak temperature appears at a lower degree of grafting when the preirradiation method is used. On the basis of these results, it is concluded that the reaction rate of radiation-induced grafting in the vapor phase depends closely upon the processes of adsorption, dissolution, and diffusion of styrene monomer in polyethylene films; in the case of simultaneous irradiation method, the reaction proceeds comparatively uniformly in the amorphous region, while in the case of the preirradiation method, the reaction proceeds mainly at the boundary of the crystalline and amorphous regions.     

PEB/MMA-AN悬浮接枝共聚反应机理

研究了乙烯-1-丁烯共聚物(PEB)弹性体与甲基丙烯酸甲酯(MMA)-丙烯腈(AN)悬浮接枝共聚反应行为及接枝共聚产物对SAN树脂增韧作用随反应时间的变化规律, 用凝胶渗透色谱法和傅里叶变换红外光谱法对接枝共聚产物进行了表征, 分析了接枝共聚反应机理, 推算了接枝链分子量. 结果表明, 体系首先发生链增长自由基向PEB转移终止形成非接枝共聚物(MAN_L)和PEB大分子自由基引发单体共聚形成接枝链(g-MAN)的反应, 接枝反应结束后体系发生明显的非接枝共聚形成非接枝共聚物(MAN_H)的反应; MAN_L的分子量低于g-MAN的分子量, 而g-MAN的分子量明显低于MAN_H的分子量; 在接枝共聚过程中发生已接枝和未接枝PEB断链并随机再接生成多嵌段共聚物的副反应; 在反应初期, 接枝链的AN单元含量接近于非接枝共聚物的AN单元含量, 在反应中后期前者远低于后者.     

ESR studies of the radiation-induced multiple graft polymerization

The radiation-induced multiple-graft polymerization was studied by an ESR method. When methyl methacrylate vapor was introduced onto preirradiated polyethylene already grafted with styrene, the second step of grafting of methyl methacrylate occurred mainly in the polyethylene portion. The kinetic treatment proved that the termination rate constant k_t of methyl methacrylate decreased with the amount of styrene grafted in advance. On the other hand, when styrene vapor was introduced onto polyethylene grafted with methyl methacrylate, only radicals of poly(methyl methacrylate) decreased. In this case, the second step of grafting of styrene occurred in the poly-(methyl methacrylate) portion which covered the whole surface of the polyethylene powder. When monomer vapors were alternately introduced onto preirradiated polyethylene powder, the second step of grafting occurred at the growing chain end of the first monomer.     

Modification irréversible de la morphologie de films de poly(chlorure de vinyle) greffés d'acide acrylique sous l'action de solvants et de la température

PVC films grafted with acrylic acid were prepared with grafting ratios as high as 160% and their swelling in N/10 KOH, was measured. An earlier observation was confirmed showing that, when the films are heated in the swollen state, they undergo an irreversible transformation which leads to an increase of their swelling ratio. A study with scanning and transmission electron microscopes showed that rigid PVC as well as PVC grafted with acrylic acid up to 27% did not exhibit any specific microstructure. At high magnifications, fibrils characteristic of fragile fractures clearly appeared on the SEM pictures. For grafting ratios of 67% or more, segregated microphases of PVC and poly(acrylic acid) are clearly seen. The size of these microphases increases after the grafted films are swollen in KOH at 60°. A systematic study with PVC films grafted to 160% showed a steady evolution of the size of the microdomains during swelling in KOH. The results explain the variations of a macroscopic property of the film (its extent of swelling) by a modification of their microstructure.     

Surface grafting of glycidyl methacrylate on silica gel and polyethylene beads

Surface grafting of glycidyl methacrylate (GMA) on silica gel and a polyethylene bead was performed by radical polymerization and radiation-induced polymerization, respectively, in order to improve softness. Subsequently, diethylene triamine (DETA), triethylene tetraamine (TETA), and iminodiacetic acid (IDA) were introduced to the grafted GMA for use as affinity columns. The efficiency of the affinity column was investigated by use of bovine serum albumin (BSA) and hemoglobin (Hb) as model proteins. The affinity degree of BSA was higher than Hb for the DETA and TETA column, whereas the affinity degree of Hb was higher than BSA for the IDA column supported by silica gel. The affinity degree of BSA was higher than Hb for the DETA and TTA column supported by polyethylene (PE) beads.     

丙烯酰胺在以N,N-二乙基二硫代氨基甲酰基修饰聚氯乙烯上的紫外光非均相接枝聚合

丙烯酰胺在以Ｎ，Ｎ 二乙基二硫代氨基甲酰基修饰聚氯乙烯上的紫外光非均相接枝聚合杨文君王永祥管建均（青岛化工学院橡塑工程研究所青岛２６６０４２）沈家骢（吉林大学化学系长春１３００２３）关键词聚氯乙烯，聚丙烯酰胺，功能高分子，接枝聚合反应，铜试剂以聚氯...     

接枝微球PMAA-HEMA/NVP对溶菌酶的吸附行为与吸附机理

采用反相悬浮聚合法制备了甲基丙烯酸羟乙酯(HEMA)与N-乙烯基吡咯烷酮(NVP)的交联共聚微球HEMA/NVP,然后采用"接出"法,实施了甲基丙烯酸(MAA)在交联微球表面的接枝聚合,制得了接枝微球PMAA-HEMA/NVP.以溶菌酶(LYZ)为模型碱性蛋白,深入研究了接枝微球PMAA-HEMA/NVP对碱性蛋白的吸附性能与吸附机理.测定了微球PMAA-HEMA/NVP的zeta电位,考察了PMAA接枝度、介质pH值及离子强度等因素对体系吸附性能的影响.结果表明,在较大的pH范围内,接枝微球PMAA-HEMA/NVP的zeta电位为绝对值较大的负值,即其表面携带有高密度的负电荷.在强静电相互作用的驱动下,接枝微球PMAA-HEMA/NVP对溶菌酶表现出很强的吸附能力.随介质pH值的增高,接枝微球对溶菌酶的吸附容量呈现先增大后减小的变化趋势,在与溶菌酶等电点接近的pH值处(pH=9),具有最大的吸附容量(90mg.g-1);离子强度对接枝微球的吸附能力也有较大的影响,当pH9时,溶菌酶吸附容量随NaCl浓度的增高而减小;当pH9时,吸附容量随NaCl浓度的增高而增大.     

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 (FTIR) 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 grafting (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 supporting membrane, as was confirmed by water contact angle testing and visualization by scanning electron microscopy.     

Greffage de l'acide methacrylique sur des films de poly(chlorure de vinyle) par la methode radiochimique directe

Since PVC films do not swell in pure methacrylic acid (MAA) the films were subjected to gamma-rays while dipped in various mixtures MAACHCl₂. Under such conditions, the grafting proceeds smoothly and its rate exhibits a flat maximum for the mixture containing ca. 50% (molar) monomer. The rate satisfies the relationship Rate = KI^0.6 and the over-all activation energy of the process is 4 kcal/mole. MAA grafted PVC films do not swell in solvents for PMAA (such as water or methanol) even for high grafting ratios. This result is unexpected since PTFE films grafted with either acrylic or methacrylic acid swell to a large extent in water and are excellent membranes. The swelling of the grafted PVC films was investigated in mixtures 1,2-dichloroethylene -methanol. It was found that the extent of swelling was highest in the mixture containing 35% methanol. The unusual swelling properties of these grafted films are attributed to strong polar interactions between PVC and PMAA chains.     

Heterogeneous grafting on polymers containing chlorine: Grafting of amide groups in water suspension and the reactivity of the new polymer towards epoxy resins

Heterogeneous grafting on polyvinylchloride suspended in water was carried out using N-butyl-3-mercaptopropionamide as nucleophile. Over 50% graft was obtained by using a small amount of solvent as a swelling agent and tricapryl methyl ammonium chloride as a phase transfer catalyst. Elemental analysis of the grafted polymer shows that the chlorine displaced from the polymers is replaced by the thio-amide group. The above conclusion is supported by NMR and IR analysis. The kinetics of the chlorine displacement from PVC by the thio amide group obeys the Shell progressive mechanism. The rate at which an individual spherical particle reacts depends on the diffusion through the reacted layer. The grafted polymer is soluble in tetrahydrofuran or nitrobenzene. The films obtained from the grafted material are brittle due to excessive internal hydrogen bonding. The electrostatic charge which is a characteristic surface phenomena in PVC is diminished in the grafted polymer which may be due to the existence of the amide group near the surface. The amide groups attached to the side chains on the polymer may participate in various reactions, e.g., with epoxy resins. IR analysis of the cured film indicates the disappearance of the oxiran band at 913 cm^?1 and an increase in the hydroxyl band around 3300 cm^?1. Thus, grafting of amide groups on PVC enables us to further modify PVC by epoxy resins.