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1-Hexene was polymerized by rac-(dimethylsilyl)bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride catalyst and methylaluminoxane cocatalyst over the temperature range 0-100 °C. The polymerization rate, polymer molecular weight, and polymer microstructure (stereospecificity and regiospecificity) were studied as a function of the temperature and the concentrations of monomer, catalyst, and cocatalyst.

The optically active epoxides (2S,3S)- and (2R,3S))-3,4-epoxy-1,2-O-isopropylidene-1,2-diols 1 and 2 were synthesized and anionically polymerized with potassium tert-butoxide as initiator. Soluble poly1's with low polydispersities (M w /M n = 1.2 - 1.3) and medium molecular weights (M n = 2000 - 5000) were obtained. Poly-2 was insoluble in common organic solvents but soluble in hot 2,2,2-trifluoroethanol. Mainchain peaks in the 13 C NMR spectrum of poly-1 were fully assigned using a combination of NMR pulse techniques. End-group peak assignments were made by controlling the type of initiation and by consideration of 13 C NMR spin-lattice relaxation times.

The zwitterion, 1-[4-[(4-hydroxy-1-naphthyl)thio]butyl]quinuclidinium hydroxide inner salt, was synthesized from tetrahydro-1-(4-hydroxy-1-naphthyl)thiophenium hydrochloride and quinuclidine and characterized by NMR and IR spectroscopy. Polymerization of the zwitterion was studied over the temperature range 175–225°C. The polymer was identified as poly(1,4-piperidinediylethyleneoxy-1,4-naphthylenethiotetramethylene) based on NMR and IR spectroscopy. The polymer was found to contain 3-butenylthio and 4-hydroxy-1-naphthyl end groups. Based on the signal area of the olefinic end group, the polymer M⌅n varied between 8500 and 13,000. The highest molecular weight was achieved at the lowest temperature, indicating that termination became more favored at higher temperature. A mechanism is proposed to describe the polymerization. © 1996 John Wiley & Sons, Inc.

The anionic bulk polymerization of optically active (2R, 3S)-3,4-epoxy-1,2-O-isopropylidenebutane-1,2-diol (1) and its (2 S, 3 S) diastereomer 2 was studied. Molecular weights and optical activity measurements as well as carbon and proton NMR spectra are reported. The polymers show solvent dependent inversion of the sign of optical rotation. The NMR spectra are consistent with isotactic polymer chains.

Various bicyclic amide acetals were synthesized from the cycloaddition reactions of 2-substituted-2-oxazolines with styrene oxide. Ring-opening polymerization of the bicyclic amide acetals occurred upon heating in the presence of methyl tosylate. Characterization of the bicyclic amide acetals and their polymers was accomplished by NMR and elemental analysis. Vapor pressure osmometry showed the highest polymer molecular weight was only 2,400. The mechanisms for cycloaddition and polymerization are discussed. © 1994 John Wiley & Sons, Inc.

The synthesis of several 3-(polyfluoro)thiophenes, which are possible precursors to conductive polythiophenes, is described. This report includes an improved synthesis of 3-trifluoromethylthiophene and the previously reported but uncharacterized 3-fluoroformylthiophene. The new compounds 1-(3-thienyl)-1H,2H,3H,3H-nonafluorohept-1-ene, 1-(3-thienyl)-1H,2H,3H,3H-tridecafluoronon-1-ene, 1-(3-thenyl)-trifluoroacetate, 1-(3-thenyl)-heptafluorobutyrate, and 1-(3-thenyl)-3-fluorosulfuryltetrafluoroethylether are reported. The last compound is unstable and decomposes to 1-fluorosulfuryl-1-fluoroformyldifluoromethane and thenyl fluoride. More extensive data for the previously prepared 1-(3-thienyl)-1H,2H,2H,3H,3H-tridecafluoronon-1-ol and 1-(3-thienyl)-1H,2H,2H,3H,3H-nonafluoroheptan-1-ol are also included.

The kinetics of radiation graft polymerization of styrene onto cellulose acetate-butyrate is studied over a range of radiation intensities and monomer concentrations. The reaction is diffusion-free under the experimental conditions as shown by the independence of the grafting rate on film thickness. The dependence of the grafting rate on monomer concentration increases from 3/2-order to slightly greater than 5/2-order with increasing radiation intensity. The dependence of the grafting rate on radiation intensity decreases from 1/2-order to 0-order with decreasing monomer concentration. Possible mechanisms for these results are discussed.

Various 4- and 4′-substitued trans-N-benlizylidenanilines were synthesized and their 1H NMR spectra recorded at 30 °C in DMSO-d6, and acidic media (TFA-d and D2SO4). The effects of substituents on the chemical shifts of H-α (proton on carbon of imine group) and H-2′ (protons on benzaldehyde ring ortho to the imine group) were analysed by the Hammett single parameter and Taft dual substituent parameter (DSP) techniques. In the neutral solvent DMSO-d6, there is transmission of the electronic effects of substituents on the benzaldehyde ring to the H-α and H-2′ protons, but no electronic transmission for substituents on the aniline ring. There is a dramatic change in acid media. Protonation of the imine group results in significant electronic transmission from substituents on the aniline ring to the H-α and H-2′ protons, as well as an enbancement in electronic transmission from substituents on the benzaldehyde ring. DSP analysis indicates that both inductive and resonance factors are responsible for the observed electronic transmission effects, with resonance being the major factor.

The Macosko-Miller approach is used to obtain an expression for the polydispersity index for AA, BB, CC linear step polymerization system in which B and C are the same type of functional group. The dependence of the polydispersity index, as a function of the extent of reaction, on the monomer masses and on the relative reactivities of B and C groups toward A, is examined in detail.

The polymerization of propylene oxide (PO) was studied with an initiator prepared by the reaction of (R)-(−)-3,3-dimethyl-1,2-butanediol (1) with aluminium hydride. When mixed with zinc chloride in a 1:1 mole ratio, the initiator was found to be highly reactive and also stereoelective in the polymerization of PO, preferentially incorporating (R)-(+)-PO into the polymer chain. Analysis of the polymer structure by 13C NMR spectroscopy showed that chlorine, hydroxyl and alkoxy end groups, derived from the initiator, were present. Fractionation of poly(propylene oxide) (PPO) in acetone at −30°Cgave about 10% insoluble PPO, shown to be isotactic by 13C NMR. The soluble, largely atactic fraction contained irregular head-to-head (h,h) and tail-to-tail (t,t) structures. In the absence of coinitiator zinc chloride the PPO product was completely soluble in acetone at −30°Cand contained a greater proportion of irregular h,h and t,t structure.

The radiation graft polymerization of styrene to polyethylene was studied under diffusion-controlled conditions of radiation intensity I, monomer concentration M1, and polymer sample thickness L. The results of the present study together with previous work under diffusion-free conditions verify our theoretical model for the diffusion-controlled reaction. The grafting rate is inverse first order in L for diffusion-controlled reaction and independent of L for diffusion-free reaction. The order of dependence of grafting rate on radiation intensity for diffusion-controlled reaction is one-half that for diffusion-free reaction. Diffusion control leads to a decrease in the order of dependence of grafting rate on monomer concentration. The decrease is greater than theoretically predicted; possible reasons for this effect are described.

The radiation-initiated graft polymerization of 4-vinylpyridine to high-density polyethylene was studied over a wide range of reaction conditions of radiation intensity I, monomer concentration M1, and polymer film thickness L. The conditions included both diffusion-free and diffusion-controlled graft polymerizations. The results corroborate our previous theoretical predictions on the effect of I, M1, and L on the experimental grafting rate. The grafting rate is inverse first order in L for diffusion-controlled reaction and independent of L for diffusion-free reaction. The dependence of grafting rate on radiation intensity decreases from 1/2 to 1/4 order for diffusion-controlled reaction. Diffusion control results in a decrease in the dependence of rate on monomer concentration. The observed decrease is somewhat greater than theoretically predicted.

A theoretical analysis has been made of the graft polymerization process in terms of the quantitative interrelationship between the initiation rate R/sub i/, the k/sub p//k/sub t/sup 1/2/ ratio of the monomer, the equilibrium solubility M of the monomer in the polymer, the polymer film thickness L, and the diffusivity D of the monomer in the polymer. It is shown how the values of these parameters in any grafting system interact to lead to diffusion controlled graft polymerization. Whether graft polymerization is diffusion-free or diffusion- controlled depends on the values of R/sub i/, D, k/sub p//K/sub t/sup 1/2/, and L as gathered in the parameter A = [(k/sub p//k/sub t/sup 1/2/)(R/sub i/sup 1/2// D)]/sup 1/2//L/2. When the values of the various terms are such that A is less than 0.1 (i.e., D is large while R/sub i/, k/ sub p//k/sub t/sup 1/2/, and L are small), the reaction is diffusion-free. When A is greater than 3 (i.e., D is small while R/sub i/, k/sub p//k/sub t/sup 1/2/, and L are large), the reaction is diffusion-controlled. The derived equations showing the relationship between kinetic and diffusional parameters are theoretically applicable to all grafting systems, i.e., for all monomer-polymer combinations under allmore » conditions of reaction temperature, radiation intensity and polymer film thickness. The theoretical analysis has been verified for the rate and degree of polymerization for the radiation-induced graft polymerization of styrene to polyethylene. (auth)« less

A general solution is presented for the kinetics of an A–A plus B–C step polymerization. B and C are the same type of functional group but with different reactivities (k1 and k2, respectively) toward A groups. The decay of the concentrations of B, C, and A groups and the increase in the degree of polymerization with time are described for various values of the ratio k2/k1.

The radiation-initiated graft polymerization of styrene onto polyethylene was studied to determine whether energy transfer to diluent was responsible for the previously observed high orders of dependence of the grafting rate on monomer concentration. n-Octane was used as the diluent instead of benzene. If energy transfer from excited polyethylene to benzene were present, it should not be with n-octane. The percent swelling of polyethylene by various n-octane–styrene mixtures was determined. The compositions of various n-octane–styrene mixtures absorbed inside polyethylene were determined by ultraviolet and refractive index measurements and found to be richer in styrene than the corresponding mixtures in which the polyethylene had been placed. The graft polymerization rates were determined at 0.000761, 0.0371, and 0.213 Mrad/hr and plotted against the inside styrene concentrations on a log-log scale to yield the kinetic orders of dependence of rate on monomer as 2,3, and 3, respectively. It was concluded that energy transfer to diluent was not responsible for the high-order dependence observed.

The radiation-initiated graft polymerization of 4-vinylpyridine to high density polyethylene has been studied under diffusion-free conditions by the mutual irradiation technique. The reaction rate is 1/2 order in radiation intensity over the range 0.00076 to 0.011 Mrad/h. The reaction rate is first order in monomer at 0.00076 Mrad/h, over the complete range of monomer concentrations; at 0.021 Mrad/h, up to 60 vol % monomer; and at 0.21 Mrad/h, up to 50 vol % monomer.

The quantitative effect of diffusion control on the rate of radiation-initiated graft polymerization has been studied theoretically for systems in which the diffusion-free reaction may show various dependencies of rate on monomer concentration other than the usual first-order dependence. The study is also very general in that it can be applied to systems involving a variety of different modes of initiation and termination. Whether the grafting process is diffusion-free or diffusion-controlled has been analyzed in terms of the interaction of the initiation rate Ri, the propagation and termination rate constants kp and kt, the equilibrium solubility M of the monomer in the polymer, the polymer film thickness L, the diffusivity D of the monomer in the polymer, and the diffusion-free kinetic order of dependence v of the grafting rate on monomer concentration. The dependence of the grafting rate for both the diffusion-free and diffusion-controlled reactions on these parameters is expressed both by mathematical experssions and graphically. Diffusion control is shown to occur at a critical value of the parameter A which is proportional to L(kpRiw/ktzD)1/2M(e−1)/2 where w, z, and v have different values depending on the specific modes of initiation, propagation and termination in a particular grafting system. The grafting rate is shown to vary with the value of A according to specific mathematical expressions. In comparing diffusion-free to diffusion-controlled reaction, it is shown that the former is independent of L and D while the latter is directly dependent on L and inversely on D1/2. Further, the change from diffusion-free to diffusion-controlled reaction involves a change in the dependence of rate on monomer from v-order to [(v − 1)/2]-order. The nonsteady-state as well as the steady-state reaction rates have been analyzed.

The diffusion-free radiation graft polymerization of styrene onto polyethylene has been studied. The grafting rate shows a dependence on monomer which is far different than what has been assumed. Further, the dependence on monomer changes with increasing dose rate as does the dependence of grafting rate on radiation dose rate. Three different regions of behavior are defined: (1) a region of low dose rate where the grafting rate is 1/2-order in dose rate and 3/2-order in monomer; (2) a region of intermediate dose rate where the grafting rate is intermediate between 1/2- and zero-order in dose rate and 5/2-order in monomer; and (3) a region of high dose rate, where the grafting rate is independent of dose rate and at least 5/2-order in monomer. Various possible mechanisms responsible for these effects are discussed, including the effects of viscosity on the initiation and termination reactions, the possibility of ionic graft polymerization, and energy transfer.

The effect of diffusion on radiation-initiated graft polymerization has been studied with emphasis on the single- and two-penetrant cases. When the physical properties of the penetrants are similar, the two-penetrant problems can be reduced to the single-penetrant problem by redefining the characteristic parameters of the system. The diffusion-free graft polymerization rate is assumed to be proportional to the upsilon power of the monomer concentration respectively, and, in which the proportionality constant a = k/sub p/R/sub i//sup w//k/sub t//sup z/, where k/sub p/ and k/sub t/ are the propagation and termination rate constants, respectively, and R/sub i/ is the initiation rate. The values of upsilon, w, and z depend on the particular reaction system. The results of earlier work were generalized by allowing a non-Fickian diffusion rate which predicts an essentially exponential dependence on the monomer concentration of the diffusion coefficient, D = D/sub 0/ (exp(deltaC/M)), where M is the saturation concentration. A reaction system is characterized by the three dimensionless parameters, upsilon, delta, and A = (L/2)(aM/sup (upsilon--1)//D/sub 0/)/sup 1/2/, where L is the polymer film thickness. Graft polymerization tends to become diffusion controlled as A increases. Larger values of delta and ..nu.. cause a reaction system to behave closermore » to the diffusion-free regime. Transition from diffusion-free to diffusion-controlled reaction involves changes in the dependence of the reaction rate on film thickness, initiation rate, and monomer concentration. Although the diffusion-free rate is w order in initiation rate, upsilon order in monomer, and independent of film thickness, the diffusion-controlled rate is w/2 order in initiator rate and inverse first-order in film thickness. Dependence of the diffusion-controlled rate on monomer is dependent in a complex manner on the diffusional characteristics of the reaction system. 11 figures, 4 tables.« less

The memory of irradiated polyethylene has been studied with emphasis on the magnitude of the restoration force exerted by the deformed polymer during the process of restoration to the nonstressed state and on the degree of completeness with which restoration occurs. The particular form of the memory effect studied has involved the deformation of the heated polymer followed by “locking-in” of the memory via cooling. Subsequent heating restores the deformed specimen to the undeformed state. The memory effect has been studied under both nontransparency (NT) and transparency (T) deformation conditions. The effects of parameters such as the polymer properties (Tm, density, molecular weight), radiation dose, and deformation and restoration conditions on the degree of restoration and restoration force have been investigated. The results of this study may be summarized as follows. Restoration temperatures equal to or above the crystalline melting point (Tm) of the polymer are required in order to obtain complete restoration. The restoration temperature increases with increasing polymer crystalline melting point. The degree of restoration increases with increasing restoration temperature for NT deformed specimens. T deformed specimens do not begin to restore until the temperature approaches the Tm of the polymer. The restoring force increases with decreasing deformation temperature. NT deformation results in larger restoring forces and faster restoration relative to T deformation. The restoring force increases with increasing radiation dose for both T and NT deformations, the effect being greater for NT deformation. Radiation dose, however, above a minimum value does not affect the degree of restoration. The restoring force increases with increasing polymer initial molecular weight for T deformation.

This paper discusses monomer reactivity ratios in various radiation- and redox-initiated graft copolymerizations. The polymers studied were polyethylene, cellulose acetate, poly(vinyl chloride), polytetrafluoroethylene, poly(vinyl alcohol), and poly(methyl methacrylate); the comonomer mixtures were styrene–acrylonitrile, methyl acrylate–styrene, acrylonitrile–methyl acrylate, and vinyl acetate–acrylonitrile. The polymer–comonomer mixture systems were so chosen as to permit study of both homogeneous and heterogeneous systems. The homogeneous systems included systems of low and high viscosity. The heterogeneous systems included both polymers swollen by the comonomer mixture and polymers not swollen by the comonomer mixture. None of the homogeneous grafting systems studied showed deviations from the normal copolymerization behavior under a variety of experimental conditions. Monomer reactivity ratios in graft copolymerization were the same as the values in nongraft copolymerization. The heterogeneous systems in which the polymer was swollen by the comonomer mixture yielded grafted copolymer compositions which were the same as those in nongraft copolymerization. The heterogeneous grafting system polytetrafluoroethylene/styrene–acrylonitrile showed deviations from normal copolymerization behavior at low degrees of grafting when the reaction was only on the polymer surface. The behavior became normal at higher degrees of grafting when the system approaches that in which the polymer is swollen by the comonomers. In all reaction systems, it was found that the use of radiation to initiate the reaction does not in any way affect the copolymerization behavior of the two monomers in a comonomer pair.

Polyfunctional monomers such as allyl methacrylate, allyl acrylate, and diallyl maleate have been found to greatly enhance the radiation crosslinking of polyethylene. The radiation dose for incipient gelation is decreased by a factor of approximately 25 by the presence of small amounts of these monomers. The ultimate scission/crosslinking ratio is unchanged by the presence of these monomers and the swelling behavior of the gels follows the Flory-Rehner equation. The monomer-crosslinking process is compared to the monomer-free process as regards the physical properties (tensile strength, elongation, modulus) of the crosslinked materials. A mechanism is presented for the enhancement of polyethylene crosslinking by polyfunctional monomers.

Gamma radioinduced surface graft copolymeridations of styrene- acrylonitrile and styrene-methyl acrylate to Teflon were studied. It was observed that the compositions of the various grafted copolymers are richer in the more polar monomer than would be predicted from the Lewis-Mayo copolymer composition equation. These results were interpreted in terms of a preferential solvation of the relatively immobile growing graft polymer free radicals by the polar monomers. (auth)

The radiation-induced graft polymerization of styrene to low density polyethylene was investigated. It was found that dilution of the styrene monomer with methanol accelerates the rate of graft polymerization with a maximum effect occurring at approximately 70 vol.-% methanol. Both the accelerated and unaccelerated graft polymerizations yield volumetric or homogeneous graft copolymers. Experiments in which n-octane was substituted for methanol as the diluent showed that the accelerative effects of methanol are best explained by the incursion of a Trommsdorff-type effect. The kp2/kt values for the grafting reaction in the various styrene-methanol solutions were calculated. It was found that the kp2/kt term is larger in grafting than in homopolymerization by a factor of 103, and that it increases as the methanol concentration of the monomer solution increases.

The effect of radiation on various propylene and ethylene–propylene copolymers has been followed by observing the gel fraction as a function of radiation dose. The G (crosslink) and β/α values were calculated from the solubility data and are discussed in terms of the polymer composition. Allyl methacrylate was found to greatly increase the efficiency of radiation crosslinking of both polypropylene and an ethylene–propylene copolymer.

It has been demonstrated that the use of solvent additives can substantially increase the rate of radiation-induced graft polymerization in the systems polyethylene–styrene, polypropylene–styrene, polyvinyl chloride–styrene, nylon–styrene, polyethylenemethyl acrylate, polypropylene–methyl acrylate, nylon–methyl acrylate. Teflonmethyl acrylate, and polyethylene–tert-butylaminoethyl methacrylate. Two different mechanisms have been shown to be responsible for the observed accelerative effects. One is the incursion of a Trommsdorff effect due to the insolubilization of the growing graft polymer chains in the solvent–monomer medium. The other mechanism is the enhancement in the degree of accessibility of monomer to grafting sites within the polymer brought about by the greater ability of the solvent additive to swell certain base polymers.