Kinetics of high-intensity electron-beam polymerization of a divinyl urethane

The kinetics of high-intensity electron beam-induced polymerization of di(2′-methacryloxyethyl)-4-m-phenylenediurethane during the network formation has been studied up to complete gelation and up to 56% conversion of unsaturation. From experimentally determined gel fractions, rate of disappearance of unsaturation, kinetic chain length, and intensity dependence, it is proposed that the polymerization takes place in a swollen network where the growing chains undergo unimolecular termination, and where gel-gel reaction is prohibited. The rate expression derived is: In [α(1 ? g)^0.545] = In α0 ? 2.51 k_ik_pt/k_t where α is the total unsaturation and g is the gel fraction. The value of k_p/k_t is found to be 2.1 and that of G_R, the free radical yield per 100 eV absorbed, to be 16; these high values are ascribed to the high viscosity of the polymerizing system.     

Graft copolymerization of 2-hydroxyethyl methacrylate and methyl methacrylate onto hide powder

Graft copolymerization of 2-hydroxyethyl methacrylate(HEMA) and mixtures of HEMA with methyl methacrylate (MMA) onto hide powder was attempted using ceric ammonium nitrate as initiator, with a view to optimize the conditions for graft copolymerization. Percent grafting and grafting efficiency were calculated for various variables such as monomer concentration, initator concentration and mole ratio of HEMA to MMA. R_p, R_g and R_h (rates of polymerization, grafting and homopolymerization respectively) were also evaluated. It was observed that R_p increased linearly with increasing concentration of MMA except at very low concentrations of the monomer. An explanation is given for the effect of variables on extent of grafting and grafting efficiency.     

Kinetics of copolymerization of methyl methacrylate and divinyl sulfide in the presence of initiating systems

The kinetics of three-dimensional radical copolymerization of methyl methacrylate and divinyl sulfide in the presence of the iniferter N,N′-bis(vinyloxyethyl)thiuram disulfide has been studied. The living chain mechanism of the process performed in the presence of the iniferter is verified by precision isothermal calorimetry. Conditions are found for more efficient kinetic parameters of the pseudoliving three-dimensional radical copolymerization of methyl methacrylate and divinyl sulfide carried out in the presence of the iniferter-AIBN initiating system. General kinetic features and differences in the pseudoliving polymerization of methyl methacrylate and its copolymerization with divinyl sulfide are ascertained.     

Kinetics of crosslinking copolymerization of styrene with symmetric divinyl compounds

Gel formation usually occurs in crosslinking systems during polymerization. The critical conversion in this process is dependent on the reactivity ratios of the different kinds of double bond in the system and on the tendency to cyclization. In this article a procedure for estimating the gel point for small amounts of a symmetric divinyl compound is shown in measurements of the degree of polymerization at different conversions. A method is also given to relate the reactivity ratio of the pendent double bonds to the amount of cyclization and to the degree of multiple crosslinking. In m-divinylbenzene/styrene the results indicate that about 10% of the pendent double bonds is consumed by cyclization due to backbiting of the primary chain, whereas an initial effective crosslink results in about seven multiple crosslink bonds.     

氢化松香与HEMA酯化物自聚与共聚研究

用氢化松香(HR)与甲基丙烯酸-2-羟乙酯(HEMA)进行酯化反应,得到了酯化物(HRH),然后对其进行了在甲苯中的自由基自聚反应、以及与甲基丙烯酸甲酯(MMA)或与苯乙烯(St)的共聚反应,制备了自聚物和共聚物,用IR和核磁共振氢谱(1HNMR)对产物进行了表征,用综合热分析仪表征了产物的热稳定性和玻璃化转变温度.结果表明:成功合成了HRH自聚物(PolyHRH)、以及共聚物[Poly(HRH-co-St)和Poly(HRH-co-MMA)].产物的热稳定性顺序为:HRH>PolyHRH>Poly(HRH-co-St)>Poly(HRH-co-MMA).     

Production of anomalous particles in the process of emulsifier-free emulsion copolymerization of styrene and 2-hydroxyethyl methacrylate

It was found that copolymer particles produced by emulsifier-free emulsion copolymerization of styrene and 2-hydroxyethyl methacrylate had an anomalous shape with uneven surface. The formation mechanism is discussed.     

Thermodynamic properties of copolymeric hydrogels based on 2-hydroxyethyl methacrylate and a zwitterionic methacrylate

The copolymerisation of 2-hydroxyethyl methacrylate and a zwitterionic methacrylate, namelyN,N-dimethyl-N-methacryloxyethyl-N-(3-sulphopropyl)-ammonium betaine (SPE), in the presence of a tetrafunctional crosslinker has been effected to 100% conversion by -irradiation. The resultant xerogels of different compositions were swollen to equilibrium in water to yield hydrogels. Volumetric swelling and compression-strain measurements were made over the temperature range 278–343 K. All these copolymers showed an increasing volumetric swelling with temperature, but the derived values of the partial molar enthalpy, entropy and Gibbs free energy of dilution showed certain differences which were interpreted on the basis of copolymer dyad distribution.     

Solution copolymerization of styrene and 2-hydroxyethyl mechacrylate.

The rate of solution copolymerization of styrene (M₁) and 2-hydroxyethyl methacrylate (M₂) was investigated by dilatometry. N,N-dimethyl formamide, toluene, isopropyl alcohol, and butyl alcohol were used as solvents. Polymerization was initiated by α,α′-azobisisobutyronitrile at 60°C. The initial copolymerization rate increased nonlinearly with increasing 2-hydroxyethyl methacrylate (HEMA)/styrene ratio. The copolymerization rate was promoted by solvents containing hydroxyl groups. Two different approaches were used for the prediction of copolymerization rates. The relationships proposed for the copolymerization rates calculation involve the effects of the total monomer concentration, mole fraction of HEMA, and of the solvent type. Different reactivity ratios were found in polar and nonpolar solvents: r₁ = 0.53, r₂ = 0.59 in N,N-dimethyl formamide, isopropyl alcohol and n-butyl alcohol; r₁ = 0.50, r₂ = 1.65 in toluene. The usability of these reactivity ratios was confirmed by batch experiments.     

Water diffusion in methacrylate based copolymer hydrogels of 2-hydroxyethyl methacrylate

The diffusion of water into cylinders of polyHEMA and copolymers of HEMA with THFMA, BMA and CHMA were studied over a range of copolymer compositions. The diffusion of water into the polymers was found to follow a Fickian, or case I mechanism. The diffusion coefficients of water were determined from mass measurements and NMR imaging studies. They were found to vary from 1.7 ± 0.2 x 10⁻¹¹ m² s⁻¹ for polyHEMA at 37°C to lower values for the copolymers. The mass of water absorbed at equilibrium relative to the mass of dry polymer varied from 52-58 wt% for polyHEMA to lower values for the copolymers.     

Copolymerisation of 2-hydroxyethyl methacrylate with siloxanyl monomers

Acryloxymethylpentamethyldisiloxane (AMS) and methacryloxymethylpentamethyldisiloxane (MMS) have been prepared and purified chromatographically. Some physicochemical properties have been measured for these monomers as well as for highly purified 2-hydroxyethyl methacrylate (HEMA). Hydroxyl group analysis on copolymers of AMS with HEMA and of MMS with HEMA, obtained by free radical copolymerisation to low conversion, enabled monomer reactivity ratios to be determined by several procedures. The average values were r_HEMA = 0.86, r_AMS = 0.55 and r_HEMA = 0.97, r_MMS = 0.33. These values have been invoked in computing integral curves for the instantaneous copolymer composition throughout the whole range of conversion.     

Synthesis of a macromonomer based on ɛ-caprolactone and 2-hydroxyethyl methacrylate

The mechanism of forming the macromonomer based on ?-caprolactone and 2-hydroxyethyl methacrylate under the effect of dibutyltin dilaurate has been investigated. The molecular-mass characteristics and the functional-type distribution of the macromonomer have been determined. It has been established that, as the concentration of the methacrylic component is increased, the contribution of side reactions related to its anionic polymerization rises. It has been shown that macromonomers with caprolactone backbones and terminal methacrylic and hydroxyl groups may be obtained. A method has been proposed for the purification of polymerization products from low-molecular-mass impurities, such as dimethacrylates and diols.     

Copolymerization of 2-hydroxyethyl methacrylate with alkyl acrylates

Copolymerization of 2-hydroxyethyl methacrylate (HEMA) with methylacrylate (MA), ethylacrylate (EA), n-butylacrylate (BA) and methylmethacrylate (MMA) were studied in bulk at 60° using benzoyl peroxide as initiator. The monomer reactivity ratios were determined using several methods and are briefly discussed.     

Copolymerizations of 2-hydroxyethyl methacrylate with alkyl methacrylates

Copolymerizations of 2-hydroxyethyl methacrylate with ethyl methacrylate and n-butyl methacrylate were studied in bulk at temperatures between 60 and 80° using benzoyl peroxide as initiator. The monomer reactivity ratios were calculated using Joshi-Joshi, Fineman-Ross and intersection methods. The temperature had only a marginal effect on the reactivity ratios.     

Kinetics of the seeded semicontinuous emulsion copolymerization of methyl methacrylate and butyl acrylate

The effect of a chain‐transfer agent (CTA) on the kinetics and molecular weight distribution of the methyl methacrylate/butyl acrylate semicontinuous emulsion polymerization was investigated. The dodecanethiol had a slight effect on the reaction rate but significantly affected the secondary nucleation. The effect of the CTA concentration on the gel formation and the effect of the reaction conditions on the mass‐transfer limitations of the CTA are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 367–375, 2000     

一种无计有机聚合物中间体——六(甲基丙烯酸羟乙酯)三聚膦腈的合成

六氯三聚膦腈;一种无计有机聚合物中间体——六(甲基丙烯酸羟乙酯)三聚膦腈的合成     

Conformational analysis of poly(2-hydroxyethyl methacrylate)

The poly(2-hydroxyethyl methacrylate) (PHEMA) is a disubstituted vinyl chain in which the substituents CO₂CH₂CH₂OH and CH₃ differ in size and shape. In order to verify the various characteristics of the PHEMA chain, the conformational energy calculations for meso and racemic diads, which are the segments consisting of the stereoregular isotactic and syndiotactic chains, respectively, were carried out using ECEPP/2 potential. From these calculations, the averaged geometry and the statistical weights were obtained in a local minima. The characteristic ratio, C∞ = (〈r²〉_o/nl²)∞, was determined from the statistical weights and geometries. The calculated C∞ for the isotactic and syndiotactic chain are 10.2 and 2.3, respectively. The characteristic ratio for isotactic chain is larger than that for syndiotactic chain. This shows that the syndiotactic chain is more folded than the isotactic chain is, and that the calculated tendency is in reasonably agreement with the experimental tendency of acrylate polymers.     

Thermal degradation of copolymers of 2-hydroxyethyl methacrylate and alkyl methacrylates

Thermal degradation of homopolymers of ethyl methacrylate (I), n-butyl methacrylate (II), 2-hydroxyethyl methacrylate (III), and copolymers of III with I and II were carried out by thermal volatilization analysis (TVA) up to 440°C with subsequent subambient thermal volatilization analysis (SATVA). An on-line mass spectrometry coupled with TVA and SATVA was employed to identify the products of thermal degradations. Isothermal pyrolyses of the polymers were carried out separately at 400°C in vacuum for 30 min and the liquid products of decomposition were collected and analysed by gas chromatography. The relationship between the amounts of I and II obtained from pyrolysis and the amounts of these components actually present in the copolymer samples was determined. Also the amount of III and ethyleneglycol dimethacrylate obtained from pyrolysis increases with the amount of III in the copolymer. The polymers were also characterized by differential thermal analysis.     

Electrospinning of the hydrophilic poly (2-hydroxyethyl methacrylate) and its copolymers with 2-ethoxyethyl methacrylate

The goal was to electrospin 2-hydroxyethyl methacrylate — based biocompatible polymers and prepare submicron fibres (nanofibers) for biomedicinal applications. Syntheses of poly(2-hydroxyethyl methacrylate) (HEMA) and its copolymer with 2-ethoxyethyl methacrylate (EOEMA), and their characterization by viscometry and molecular weight are described. Their relation to electrospinning is discussed. Electrospinning of HEMA homopolymer from water-ethanol is successful for molecular weights 6.31 × 10⁵ and 1.80 × 10⁶ g/mol. Electrospinning of HEMA/EOEMA copolymers is feasible from ethanol.      

Low-temperature radiation-induced copolymerization of N-vinylpyrrolidone with divinyl sulfone

The low-temperature copolymerization of N-vinylpyrrolidone with divinyl sulfone was studied in vitrifying dimethylformamide solutions. It was shown that the copolymerization proceeds efficiently in a viscous supercooled liquid after devitrification of the system. The mechanism and conditions are determined for the formation of random and alternating copolymers.     

The thermorheological complexity of photoelastic behaviour of 2-hydroxyethyl methacrylate — dodecyl methacrylate copolymers

The viscoelastic photoelastic behaviour of networks of 2-hydroxyethyl methacrylate — dodecyl methacrylate (DMA) copolymers in the main transition and rubberlike region was investigated. With increasing DMA content, photoelastic functions are quickly shifted to lower temperatures or shorter times; a detailed course of the functions suggests heterogeneity of the copolymers. Due to the existence of long side chains, optical function of all samples change the sign from positive to negative with increasing temperature. While the temperature dependences of the moduli of copolymers can be described by the two-phase Takayanagi model, the temperature dependences of optical functions cannot be described by using this model. It has been found, however, that the tempeature and time dependences of photoelastic functions can be described semiquantitatively by a three-phase model with a hypothetical statistical copolymer as the third component. The high values of the volume fraction of the hypothetical statistical copolymer found for the individual samples, suggest a considerable miscibility and a strong influence of the interphase boundary on the photoelastic behaviour of the copolymers.