Controllable surface modifications of polyamide by photo‐induced graft polymerization using immobilized photo‐initiators

A novel two‐step UV initiated grafting method has been developed and applied on surface modification of polyamide. Anthraquinone‐2‐sulfonate sodium, an acid dye, was chosen as the photo‐initiator. In the first step, photo‐initiators were ionically bonded onto polyamide through a normal acid dye dyeing process. Vinyl monomers such as acrylic acid were then grafted onto polyamide surface in the following step. During UVA irradiation, not only monomers were grafted onto polymer surface, photo‐initiator itself was also covalently bonded onto polymer. The grafted polymers were characterized by Fourier transform infrared spectrometer (FTIR), X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).The degree of photo‐grafting can be controlled by adjusting concentrations of photo‐initiator and monomer, as well as UVA exposure time. This process demonstrated the feasibility of efficiently modifying polymer surface under low UV intensity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Spectrofluorometric analysis and electrical conductivities of styrene and methyl methacrylate polymers

Conductive polymers were obtained by using a new polymerization method where UV‐light was used as a photochemical initiator. To obtain high molecular weights, optimum irradiation times were determined. The luminescence properties of polymers have been found to be useful for their identification. The use of luminescence spectroscopy as an analytical technique for polymer identification involves the measurement of fluorescence emission spectrum, which is obtained by exciting the polymer with UV‐radiation. Fluorescence emission spectra of polystyrene (PS) and polymethyl methacrylate (PMMA) samples were taken at room temperature at excitation wavelengths at 290 nm and 292 nm, respectively. PPMA was prepared with different molecular weights, and the intensity of the fluorescence emission was correlated with polymer chain length. Conductivity versus molecular weight relation was established for each polymer. The plots obtained between conductivities and molecular weights can be used as a calibration curve. From the plot of emission intensity against polymer molecular weights, the molecular weights of unknown polymeric samples can be determined. The most efficient irradiation times were determined by using conductivity versus irradiation time plots. Conductivity versus temperature change of the polymeric samples at different temperatures was determined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

微波辅助法合成高分子量聚丙烯酰胺

以丙烯酰胺(AM)为单体,水为溶剂,过硫酸铵(APS)和偶氮二异丁基脒盐酸盐(AIBA)为复合引发体系,采用微波辅助法制备聚丙烯酰胺(PAM)。研究了微波辐照功率、辐照时间、单体浓度、引发剂用量对聚丙烯酰胺分子量和单体残留率的影响,采用红外光谱(FT-IR)表征了聚合物产物结构,最后考察了剪切作用对PAM性能的影响。结果表明:采用微波辅助法制备的PAM反应时间短、能耗低、分子量高、单体残留率低;当微波功率为100 W,辐照时间为8 min,单体浓度为25%,引发剂用量为0.05%时产物分子量可达1050×104,并且单体残余量低;PAM的降解随着剪切时间的延长和剪切速度的加快而加快。     

黄原胶辐射接枝丙烯酸及其耐盐性研究

以60Coγ为辐射源,对黄原胶(XG)和丙烯酸(AA)进行共辐射制备黄原胶/丙烯酸接枝共聚物(XG-g-PAA)。研究了合成条件对产品接枝性及吸水性的影响,并和化学引发得到的接枝物的吸水性及耐盐性进行了比较,用红外光谱及电镜扫描对产品结构进行了表征。结果表明,产品接枝率为130.8%,接枝效率为82.4%,吸去离子水率为815 g/g。它在去离子水、人工尿及质量分数均为0.9%的NaCl水溶液、BaCl2水溶液、FeCl3水溶液、Na2SO4水溶液、尿素水溶液中的吸水率,较经化学引发得到的接枝物分别提高了45.3%、27.3%、20.6%、16.7%、10.2%、20.7%、44.9%。SEM表明,辐射引发较化学引发更易得到多孔疏松的产品,该产品是农用保水剂及卫生用品的良好候选材料。     

Synthesis and solution properties of poly(acrylamide-styrene) block copolymers with high hydrophobic content

Hydrophobically associating block copolymers of polyacrylamide/styrene with a high hydrophobe content were synthesized using micellar copolymerization under various conditions of surfactant and initiator concentrations with the objective of determining the conditions that produce optimum solution properties for enhanced oil recovery. Solubilities, aqueous solution viscosities and interfacial properties with air and oil of the copolymers were investigated. The influence of salt on the solution properties was also studied. Nature of hydrophobic sites and onset of hydrophobic association were studied by measuring the fluorescence of pyrene in polymer solutions. Optimum solution properties were obtained for copolymers synthesized under conditions of high surfactant and initiator concentrations. The copolymers displayed substantial thickening properties at low concentrations with enhanced thickening in the presence of salt. The interfacial tensions of the aqueous solutions with n-decane and air were also reduced. Interfacial properties were slightly sensitive to salt concentration. The copolymer solutions showed shear and temperature thinning behaviors typical of polymer solutions.     

Combined reactive extrusion–orientation of polyethylene

The objective of this work is to combine reaction, extrusion, and orientation together in a process so as to provide product in a form which is not limited to fiber or film. Three coupled problems form the focus of the work: (i) devising a practical, continuous extrusion-orientation method; (ii) generating low concentrations of free radicals in the polymer to tailor molecular weight distribution before orientation; (iii) generating high concentrations of free radicals in the polymer to form a network in the oriented polymer without destroying its superior properties after orientation. A continuous extrusion method for orienting polymer in forms other than fibers and films was devised based upon two melt pullers. Operation of a prototype of the equipment showed it capable of providing draw ratios of greater than ten. Injection of low initiator concentrations during extrusion (i.e., before orientation) directed at solving the second problem had an effect which depended upon the degree of branching, the molecular weight, and the degree of unsaturation of the polyethylene. Large increases in molecular weight could be obtained. However, in agreement with previous work, formation of branched molecules drastically limited draw ratios attainable by the extrusion-orientation process. To obtain high concentrations of free radicals, bench scale experiments demonstrated that a recently published method involving the use of a UV sensitizer and crosslinker followed by irradiation was directly adaptable to this process (with the irradiation applied after orientation) and provided significant improvements in creep resistance. Various attempts involving die design to obtain orientation and high initiator concentrations as well as gamma radiation to induce crosslinking after orientation were attempted and appear far less promising than the above methods.     

Grafted chain as spacer for an insoluble polymer ligand. II. Two-step polymerization using tetraethylthiuram disulfide as an initiator

In order to increase the percent grafting in the graft polymerization of chloromethylstyrene onto a crosslinked polystyrene bead with UV light irradiation, a two-step polymerization consisting of a suspension polymerization of styrene containing divinylbenzene using tetraethylthiuram disulfide as an initiator and then a subsequent graft polymerization of chloromethyl-styrene onto the crosslinked polystyrene bead was carried out. The percent grafting of up to 180% was obtained, the value being about twofold larger than that for the usual method using benzoyl peroxide as an initiator. The higher percent grafting was found to result from the higher grafting efficiency due to the preferential decomposition of diethyldithiocarbamate group in the crosslinked polystyrene bead with UV light irradiation. The chloromethyl group in the grafted chain was converted to aminomethyl group, and then to the iminodiacetic acid group, which was a ligand group. The adsorption behavior of Cu(II) by the ligand polymer and the catalytic activity of the complex in the decomposition of hydrogen peroxide were examined, and both properties were found to be improved by introducing grafted chain as spacer, especially markedly at a higher percent grafting.     

Water‐soluble copolymers. II. Inverse emulsion terpolymerization of acrylamide,sodium acrylate,and acryloyloxyethyl trimethylammonium chloride

Inverse emulsion terpolymerization of acrylamide, sodium acrylate, and acryloyloxyethyl trimethylammonium chloride was investigated. Aqueous monomer solutions were emulsified in diesel oil with a blend of two surfactants (SPAN80 and TWEEN80) using 2,2′‐azobis(2‐amidinopropen)‐dihydrochloride as the initiator. The effects of temperature, initiator concentration, monomer concentration and composition, and emulsifier content on the polymerization conversion and the polymer intrinsic viscosity were examined. Polymer intrinsic viscosity increased with a decreasing concentration of initiator and an increasing concentration of monomer. The sizes of the latex particles of the terpolymer emulsions were observed with a scanning electron microscope, and the structure of the terpolymer was identified by FTIR spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1381–1385, 2006     

Preparation of Conjugated p-Aminobenzamidine on Thermosensitive Poly(NIPAM) by Irradiation Grafted Process

A thermosensitive polymer that can either be soluble or insoluble in water was synthesized by electron beam irradiation N-isopropylacrylamide (NIPAM) and β-mercaptopropionic acid (MPA) without the presence of initiator. The polymer was then reacted with p-aminobenzamidine (PABA) using water-soluble carbodiimide (WSC) to introduce an affinity ligand. Radiation grafting of poly(NIPAM) and conjugation of ligand was successfully completed. It was found that the graft reaction could be done at higher dose and carboxyl group was introduced during irradiation of samples in air. Production and precipitate of the carboxylated poly(NIPAM) were investigated. Some results of direct radiation polymerization in this system are also given. The effect of radiation characteristics such as irradiation dose on the lower critical solution temperature (LCST) and conjugation of PABA on the prepared poly(NIPAM) has also been investigated. The precipitate of the grafted polymer has thermal sensitivity and their LCST is close to 35°C.     

Precipitation of PMMA/PCL blends using supercritical carbon dioxide

Solutions of a poly(methyl methacrylate)–poly(ε‐Caprolactone) (PMMA/PCL) polymer blend in dichloromethane (DCM) and mixtures of the same polymer blend and cholesterol in DCM were sprayed into supercritical carbon dioxide. Carbon dioxide was contacted with 0.23–1 wt % polymer solutions and with 0.3–1 wt % polymer plus 0.1–0.6 wt % cholesterol solutions in a continuous mode of operation. Pressure and temperature were constant for almost all of the experiments, 11 MPa and 314 K, respectively. Fibrous networks composed of many smaller microfibrils were obtained by spraying the different solutions through a conical nozzle into concurrently flowing supercritical carbon dioxide. This morphology suggests such an important degree of agglomeration that primary particles are no longer discernible. Processing the polymers with CO₂ leads to the removal of contaminants as the precipitate was free of monomer and initiator. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2422–2426, 2004     

Emulsion polymerization of styrene under pulsed microwave irradiation

We performed the emulsion polymerization of styrene successfully with potassium persulfate (KPS) as an initiator and sodium dodecylsulfonate as an emulsifier under high‐power pulsed microwave irradiation (PMI). We investigated the effects of the temperature, the concentration of initiator, and various parameters of PMI (i.e., irradiation power, duty cycle, irradiation energy, and pulse width) on the polymerization. The results indicated that PMI, compared to conventional heating (CH), caused a significant increase in the decomposition rate of KPS (2.4 times higher than that under CH at about 70°C) and in the amount of particles (5 times higher than that under CH); consequently, the polymerization rate was effectively enhanced. For initiator concentrations of 0.10 and 0.20 wt %, the enhancement of the polymerization rate under PMI was 129 and 38% greater, respectively, than that under CH. The glass‐transition temperature and the regularity composition of the polymers under PMI and CH showed no difference, which indicated that PMI had little effect on the physical properties and microstructure of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 28–35, 2003     

Effect of Polymerization Conditions on the Rheological Behavior of Acrylic Polymer Solutions with 1-Butyl-3-Methylimidazolium Tetrafluoroborate as Solvent

Rheological behavior of concentrated acrylic polymer/1-butyl-3-methylimidazolium tetrafluoroborate (PAN/[BMIM]BF4) solutions, which were prepared by the radical copolymerization of acrylonitrile (AN) and methylate (MA) in ionic liquid, is reported. The effect of copolymerization conditions on the rheological behavior of the solutions is discussed in detail. The shear viscosity and structural viscosity index, Δη, increases while the non-Newtonian index, n, decreases with increasing polymer concentration as the copolymerization time increases, and decreases with decreasing initiator concentration. It is shown that the rheological behavior of PAN/[BMIM]BF₄ can be directly controlled by varying copolymerization conditions.     

The inverse emulsion polymerization of acrylamide with pentaerythritolmyristate as emulsifier. 1. Experimental studies

The inverse emulsion polymerization of aqueous acrylamide solutions in isooctane as dispersing media with the emulsifier pentaerythritolmyristate and an oil-soluble azo initiator was studied, particularly with respect to the influence of the chemically pure emulsifier. In this free radical polymerization, a water-in-oil emulsion with droplet sizes around 10μm is converted into a latex with average particle diameters between 80 and 200nm containing a polymer with molar masses up to 16×10⁶gmol^-1 Kinetic data were measured by adiabatic as well as by isothermal calorimetry. The influences of various parameters on polymerization kinetics, particle numbers and molar mass averages were studied. Experimental results show a positive influence of the emulsifier concentration on the reaction rate and indicate the dominance of a bimolecular termination re-action with respect to the polymer radicals above a certain initiator concentration. © 1998 SCI.     

UV-assisted synthesis of super-macroporous polymer hydrogels

A facile method to the synthesis of polymer cryogels employing the UV irradiation technique and hydrogen peroxide as initiator is presented. Various cryogels composed of either biocompatible, biodegradable and/or temperature-responsive polymers are synthesized from polymer or monomer precursors. It is found that due to the macroporous structure, the cryogels exhibit a very rapid water uptake and, in the case of temperature-responsive polymers, ultra-rapid volume phase transition. The immobilization of Ag nanoparticles (Ag NPs) into cryogels by two different approaches allows preparation of hybrid systems possessing either very fast release of Ag NPs or very slow release of Ag⁺.     

Estimation of transfer constants in the aqueous solution polymerization of acrylamide with potassium persulfate initiator

An experimental investigation on the aqueous polymerization of acrylamide with potassium persulfate initiator is reported. Molecular weight averages were measured by viscometry. Non-Newtonian effects were accounted for by extrapolation to high shear rates where the polymer solutions approximated Newtonian behavior. Values for the transfer constants to the acrylamide monomer and to the persulfate initiator were estimated at 25 and 40°C and compared to literature values.     

Preparation of stimuli‐responsive nanogels of poly [2‐(dimethylamino) ethyl methacrylate] by heterophase and microemulsion polymerization using gamma radiation

Poly [2‐(dimethylamino) ethyl methacrylate], PDMAEMA, was synthesized by heterophase polymerization at 70°C using sodium dodecylsulfate (SDS) as stabilizer and potassium persulfate (KPS) as the initiator. Conversions were 60%, polymer content 18%, and intensity average particle diameter, D_p, 32 nm. γ‐rays irradiation of PDMAEMA nanolatexes and DMAEMA/H₂O/SDS microemulsions using ethyleneglycol dimethacrylate produced nanogels responding to temperature and pH. Nanogels shrinked as temperature increased, swelled excessively in acidic solutions (maximum D_p: 498 nm) and deswelled (minimum D_p: 257 nm) in basic solutions for the case of the nanogels obtained from PDMAEMA nanolatexes. pH response to swelling is due to protonation of amine groups in the backbone of PDMAEMA in acidic conditions leading to electrostatic interactions in the nanogel. POLYM. ENG. SCI., 54:1625–1631, 2014. © 2013 Society of Plastics Engineers     

Preparation,characterization, and properties of cellulose–polyacrylamide graft copolymers

Graft copolymers of acrylamide on cellulose materials (α‐cellulose 55.8%, DP 287.3) obtained from Terminalia superba wood meal and its carboxymethylated derivative (DS 0.438) were prepared using a ceric ion initiator and batch polymerization and modified batch polymerization processes. The extent of graft polymer formation was measured in graft level, grafting efficiency, molecular weight of grafted polymer chains, frequency of grafting as a function of the polymerization medium, and initiator and monomer concentrations. It was found that the modified batch polymerization process yielded greater graft polymer formation and that graft copolymerization in aqueous alcohol medium resulted in enhanced levels of grafting and formation of many short grafted polymer chains. Viscosity measurements in aqueous solutions of carboxymethyl cellulose‐g‐polyacrylamide copolymer samples showed that interpositioning of polyacrylamide chains markedly increased the specific viscosity and resistance to biodegradation of the graft copolymers. The flocculation characteristics of the graft copolymers were determined with kaolin suspension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 913–923, 2003     

PEGDA交联PAA-K高吸水树脂制备及性能研究

采用紫外引发、微波引发方法分别制备聚丙烯酸钾(PAA-K)高吸水树脂,研究了交联剂聚乙二醇二丙烯酸酯(PEGDA)、光引发剂2,2二甲氧基苯基乙酮(BDK)、引发剂过硫酸铵(APS)以及丙烯酸(AA)中和度对PAA-K高吸水树脂吸水性能的影响以及两种方法制备PAA-K树脂性能的比较。采用傅里叶变换红外光谱仪、热失重分析仪、扫描电子显微镜等仪器对PAA-K高吸水树脂进行表征。结果表明,在最佳优化条件下,紫外引发PAA-K高吸水树脂在蒸馏水和生理盐水中的最大吸水倍率分别为3297 g/g和419 g/g;微波引发PAA-K高吸水树脂在蒸馏水和生理盐水中的最大吸水倍率分别为2861 g/g和414 g/g。     

大粒径磁性高分子微球的合成

本文研究了苯乙烯、丙烯酸等单体在磁性氧化铁(E_((?)3)O_4)的醇/水分散体系中的聚合行为。为了改善磁性氧化铁粒子与苯乙烯单体间的亲合性,加入聚乙二醇作为分散剂和稳定剂,制备出粒径为30～1000μm的具有磁响应性的聚苯乙烯微球。研究了控制聚合区域的方法,考察了分散稳定剂、分散介质、引发剂种类和用量、反应时间等因素对聚合行为及微球形成的影响。     

Coumarin end-capped polystyrene by ATRP and photodimerization reaction

Summary New coumarin-end-capped polystyrenes have been prepared using functional initiators by atom-transfer radical polymerization (ATRP). In the first case, the photosensitive initiator, 7-chloroacetoxy-4-methyl-coumarin, was prepared. Then the styrene was initiated by 7-chloroacetoxy-4-methyl-coumarin in the presence of a CuBr/bipyridine. The functionalization of the polymers was nearly quantitative, the molecular weight and structure were well controlled by adjusting the monomer/initiator molar ratio, polymerization temperature and time. At high monomer conversion, the polydispersity index of polymer was about 1.40. These coumarin-end-capped polystyrenes underwent [2+2] cycloaddition reaction under UV irradiation in film state. After irradiation the molecular weight and polydispersity index of polystyrene both increased, but the maximum molecular weight was less than the double of original one. It means that the photodimerization reaction was not complete throughly in film state for the diffusion of coumarin groups was blocked by polymeric chain entanglement.