Distribution of polymer deposition in plasma polymerization. III. Effect of discharge power

Distribution of polymer deposition in an inductively coupled rf discharge system is studied as a function of level of discharge power with acetylene and styrene as monomers. When a fixed flow rate is used, the discharge power has a relatively small effect on the pattern of distribution of polymer deposition as long as values of W/FM, where W is discharge wattage, F is flow rate, and M is molecular weight of monomer, are maintained above a critical level to maintain full glow in the reaction tube. It has been shown that plasma polymerization of two monomers which have different molecular weights can be compared in a fair manner by selecting conditions to yield similar value of W/FM.     

Distribution of polymer deposition in plasma polymerization. II. Effect of reactor design

The effects of relative positions of the monomer inlet and the r.f. coil, and of the inlet and outlet, on the distribution of polymer deposition in plasma polymerization of ethylene were investigated using an electrodeless glow discharge by a 13.5-MHz radiofrequency source. The diffusional transport of active species created under the r.f. coil, diffusional transport of polymer forming species, and flow of gas in the system are important factors that determine the distributions of polymer deposition observed in plasma polymerization of ethylene. The mechanisms of polymer deposition are discussed in conjunction with postulated plasma polymerization mechanisms.     

Radiation-induced emulsion polymerization of ethylene. I. Effect of reaction conditions on the polymerization

The effect of reaction conditions on the rate of radiation-induced emulsion polymerization of ethylene was studied by use of a 500-ml autoclave. Among various kinds of emulsifiers, a series of potassium salts of fatty acids gave high rates of the polymerization. The polymerization was inhibited by the presence of oxygen, but the rate of polymerization followed by the induction period was not influenced by the initial presence of oxygen. Stirring rate and the monomer: water ratio did not affect the rate of polymerization. The rate of polymerization was maximum at about 80°C, and number-average molecular weight was influenced by the temperature in a similar manner as the rate of polymerization. This suggests that the change of mobility of propagating radical in the polymer particle changes the rate of termination reaction. The rate of polymerization was proportional to the 1.7 power of the reaction pressure.     

Anionic graft polymerization of ethylene oxide on starch. I

Graft polymers of polyethylene oxide on various starches were obtained by anionic graft polymerization of ethylene oxide on the starch alkoxide derivatives. The polyalkoxides were prepared by reaction of potassium naphthalene with starch in DMSO solution. It was found that increase of monomer or alkoxide concentration led to transformation of the grafts from solids to syrups. Rice starch, having a more complex structure than soluble starch or wheat starch, led to graft polymers having higher melting ranges than the others. The graft polymers were very soluble in water or methanol.     

Chain transfer in ethylene polymerization. V. The effect of temperature

In order to determine the effect of temperature on the chain-transfer reaction in the free-radical polymerization of ethylene, chain-transfer constants were measured for sixteen transfer agents at 130°C and 200°C at 1360 atm. The results were interpreted as ΔE*, the activation energy of the chain-transfer constant. This value is equal to the difference in activation energy between the transfer step (hydrogen abstraction) and the propagation step (addition to the monomer double bond): ΔE* = E_s* ? E_p*. Excellent agreement was found between measured ΔE* values determined at 1360 atm pressure and (E_s* ? E_p*) data for ethyl radical determined in vacuum gas-phase reactions. Apparently, the ethyl radical is a good model for polyethyl radical. The chain-transfer constant of ethylbenzene was found to be insensitive to temperature changes, indicating that E_p* = E_s* for this compound.     

Chain transfer in ethylene polymerization. VI. The effect of pressure

The chain-transfer reaction, which controls the molecular weight level of the polymer, apparently has not been studied as a function of pressure for ethylene. Therefore, the chain-transfer constants for eleven transfer agents were determined at 1360 and 2380 atm at 130°C. The results were interpreted according to transition-state theory as the difference between the volumes of activation for the transfer and propagation steps. It was found that the effect of pressure on the transfer constant is small for most transfer agents, indicating that the volumes of activation for hydrogen abstraction and addition to the ethylene double bond are similar. Aralkanes, however, gave anomalous results.     

The effect of ion energy upon plasma polymerization deposition rate for acrylic acid

A novel technique, which allows the importance of ion energy in plasma polymer film growth to be investigated, without perturbation of any other plasma parameter (particle densities or temperatures) or, in principle, perturbation of particle (neutral or ion) fluxes is applied in the plasma polymerisation of acrylic acid and new insight into polymer formation is gleaned.     

Photoconduction in poly(ethylene terephthalate). I. Mechanisms of carrier generation

Mechanisms of photocarrier generation in poly(ethylene terephthalate) (PET) have been investigated. In the wavelength range of λ ≦320 nm, the photocurrent spectra correspond closely with the optical absorption spectra of PET and the assignment of the absorption peaks revealed that photocarriers are generated through ππ^* excitations. In the wavelength range from 320 to 400 nm, photocarriers are injected from metal electrodes. The threshold energies for Al and Cu electrodes are 2.8₇ and 2.9₄ eV, respectively, indicating the presence of surface states. The simplified model gives the density of the surface states as 1.7 × 10¹⁴ cm^?2 eV^?1.     

Radiation-induced emulsion polymerization of ethylene. II. Effect of potassium myristate concentration and dose rate on the rate of polymerization in connection with polymer properties,kinetics, and mechanism

Radiation-induced emulsion polymerization of ethylene with potassium myristate as an emulsifier was studied in connection with the kinetics and the mechanism. The molecular weight of polymer was relatively low, of the order of 10³, when a sufficient amount of emulsifier was used. However, polyethylene gel was produced in the absence of a sufficient amount of emulsifier. The rate of polymerization was proportional to the 0.5 power of dose rate and increased slightly with increasing emulsifier concentration. The rate of seeded polymerization followed a similar trend to that for conventional polymerization. Kinetic analysis of these results suggests that the escape of radicals produced by chain transfer of propagating radical with the emulsifier and the monomer from polymer particles into the aqueous phase plays an important part in the rate of polymerization. The melting temperature and the crystallinity of the polymer significantly decreased with increasing polymerization temperature in the range 40–60°C.     

Block copolymers of styrene,isoprene, and ethylene oxide prepared by anionic polymerization. I. Synthesis and characterization

Anionic polymerization has been used as a technique for the synthesis of five-block copolymers of polystyrene (PS), polyisoprene (PI), and poly(ethylene oxide) (PEO). Two types of such polymers, PEO-PI-PS-PI-PEO and PEO-PS-PI-PS-PEO with varying PEO block length, have been prepared, using potassium naphthalene as the initiator and tetrahydrofuran as the solvent. The polymers were purified by extraction with ethyl acetate, diethyl ether, and water. After the addition of each monomer, a sample from the living polymer solution was taken and analyzed by spectroscopy (infared (IR) and proton magnetic resonance (PMR)), osmometry, and gel-permeation chromatography (GPC) to obtain information about composition, molecular weight and molecular weight distribution of the intermediate polymers. The five-block copolymers have also been characterized by the same techniques and by elemental analysis.     

Studies of ziegler-type catalysts for the polymerization of ethylene and propylene—I a highly active catalyst for the polymerization of ethylene

The reaction product of an incompletely desolvated ethereal Grignard reagent and TiCl₄, when employed with a trialkylaluminium cocatalyst, possesses catalytic activity for the polymerization of ethylene, of some two orders of magnitude (on the basis of Ti) greater than that of traditional TiCl₃ catalysts. The yield of polyethylene increases linearly with increasing ⁱBu₃Al concentration, when a constant amount of Et,Zn is also present.     

Emulsion polymerization of acrylonitrile. Part I. Role and effect of emulsifiers in the emulsion polymerization of acrylonitrile

The role in and effects on the emulsion polymerization of acrylonitrile (AN) of three different groups of emulsifiers, i.e., low molecular emulsfiers, well-known water-soluble polymers, and new water-soluble polymers containing a sulfonate group have been investigated by a dilatometry and electron microscopy. The major part of this paper concentrates on the study of the relation between the properties of the third group of emulsifiers and emulsion polymerization characteristics of AN such as rate, degree of polymerization, diameter and number of particles, and the degree of dispersion, by adding copolymers of AN and sodium p-styrenesulfonate (SSS) having various compositions. In the emulsion polymerization of AN, the hydrophobic portion of the emulsifier seems to act as a kind of nucleus around which polymer molecules precipitate and particle formation may occur, and the hydrophilic portion stabilizes the polymer particles thus formed. As the number of particles and the degree of dispersion increases, the total surface of the particles increases, which may raise the overall rate of polymerization due mainly to an increased polymerization on the surface of the polymer particles. The well-known emulsifiers may be classified by the properties and ratio of the nucleus portion and the stabilizing portion. The unusual effect of emulsifiers on the degree of polymerization may be explained by a chain-transfer mechanism.     

Synergistic effect and fluorination effect in ethylene polymerization by nickel phenoxyiminato catalysts

A series of binuclear nickel phenoxyiminato catalysts with different linkers and fluorine substituents were efficiently synthesized.Binuclear nickel catalysts with rigid linkers showed higher catalytic activity and thermal stability in ethylene polymerization and produced polymers with higher molecular weight possibly due to the larger steric hindrance and metal-metal synergistic effect.The introduction of fluorine atoms on the N-terphenyl moity also enhanced polymerization activity and molecular weight of polymer due to the electronic effect of fluorine atoms.     

Radiation-induced emulsion polymerization of ethylene. IV. Effect of pressure,temperature, and additives on rate in connection with number of polymer particles

The effects of pressure, temperature, and additives on the rate of radiation-induced emulsion polymerization of ethylene with FC-143 as emulsifier were studied kinetically. The rate of polymerization was proportional to the 2.5 power of ethylene fugacity, and the apparent rate constant (rate of polymerization/2.5 power of ethylene fugacity) was constant below 78°C. Above this temperature, the rate constant decreased with an apparent activation energy of ?8.2 kcal/mole. These facts can be interpreted in connection with the polymer structure and the change of rate of escape of radicals from the polymer structure and the change of rate of escape of radicals from the polymer particle into the aqueous phase. The rate of polymerization decreased on addition of a series of n-aliphatic alcohols due to the chain-transfer reaction and consequent escape of radicals to the aqueous phase. On the other hand, the addition of tert-butyl alcohol increased the rate of polymerization, probably because of its effect in increasing swelling of the polymer particles. Addition of electrolytes increased the rate of polymeriaztion as a result of the increase of the number of polymer particles.     

Reactive oligomers. I. Preparation and polymerization of ethylene glycol bis(methyl fumarate)

Ethylene glycol bis(methyl fumarate) (EGBMF) was prepared as a new type of divinyl compound and reactive oligomer: a needle crystal, m.p. 104.5°C. Homopolymerization of EGBMF was carried out in dioxane with 0.1 mol/L AIBN at [M] = 1 mol/L and 60°C; the rate of polymerization was estimated to be 4.44 × 10^?6 mol/L s in a good agreement with diethyl fumarate (DEF). The cyclization constant K_c was obtained as 1.64 mol/L, being rather low compared with diallyl oxalate which is 1,9-diene having two ester groups analogous to EGBMF. Gelatin occurred at about 35% conversion. Finally, the copolymerization of EGBMF (M₁) with diallyl phthalate (DAP) (M₂) is tentatively explored with the intention of the improvement of allyl resins in mechanical properties; remarkable rate enhancement was observed for copolymerization. The monomer reactivity ratios were estimated to be r₁ = 0.96 and r₂ = 0.025, the r₁ value being reduced compared with the DEF-DAP copolymerization system. These results are discussed from the standpoint of steric effect on the polymerization of fumarate as an internal olefin.     

Some aspects of plasma polymerization of fluorine-containing organic compounds. II. Comparison of ethylene and tetrafluoroethylene

Plasma polymerizations of ethylene and tetrafluoroethylene are compared. In the plasma polymerization of ethylene and of tetrafluoroethylene, glow characteristics play an important role. Glow characteristic is dependent on a combined factor of W/F_m, where W is discharge power and F_m is monomer flow rate. At higher flow rates, higher wattages are required to maintain “full glow.” In the plasma polymerization of tetrafluoroethylene, simultaneous decomposition of the monomer competes with plasma polymerization. Above a certain value of W/F_m, decomposition becomes the predominant reaction, and the polymer deposition rate decreases with increasing discharge power. ESCA results indicate that the plasma polymer of tetrafluoroethylene that is formed in an incomplete glow region (low W/F_m) is a hybrid of polymers of plasma polymerization and of plasma-induced polymerization of the monomer. Polymers formed under conditions of high W/F_m to produce “full glow” are similar, regardless of the extent of decomposition of the monomer. They contain carbons with different numbers of F(CF₃, ? CF₂? , >CF? , >C<) and carbons bonded to other more electronegative substituents.     

Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. I. Effects of reaction conditions on the polymerization rate and polymer molecular weight

The radiation-induced emulsifier-free emulsion polymerization of tetrafluoroethylene was carried out at an initial pressure of 2–25 kg/cm², temperature of 30–110°C, and under a dose rate of 0.57 × 10⁴?3.0 × 10⁴ rad/hr. The rate of polymerization was shown to be proportional to 1.0 and 1.3 powers of the dose rate and initial pressure, respectively, and is maximal at about 70°C. The molecular weight of polytetrafluoroethylene (PTFE) lies in the range of 10⁵?10⁶, increases with reaction time in the early stage of polymerization, and is maximal at 70°C but is almost independent of the dose rate. An interesting discovery is that PTFE, a hydrophobic polymer, forms as a stable latex in the absence of emulsifier. When PTFE latex coagulates during polymerization under certain conditions, the polymerization rate decreases, probably because polymerization proceeds mainly on the polymer particle surface. The observed rate acceleration and successive increase in polymer molecular weight may be due to slow termination of propagating radicals in the rigid PTFE particles.     

Preparation of macroporous functionalized polymer beads by a multistep polymerization and their application in zirconocene catalysts for ethylene polymerization

Macroporous functionalized polymer beads of poly(4‐vinylpyridine‐co‐1,4‐divinylbenzene) [P(VPy‐co‐DVB)] were prepared by a multistep polymerization, including a polystyrene (PS) shape template by emulsifier‐free emulsion polymerization, linear PS seeds by staged template suspension polymerization, and macroporous functionalized polymer beads of P(VPy‐co‐DVB) by multistep seeded polymerization. The polymer beads, having a cellular texture, were made of many small, spherical particles. The bead size was 10–50 μm, and the pore size was 0.1–1.5 μm. The polymer beads were used as supports for zirconocene catalysts in ethylene polymerization. They were very different from traditional polymer supports. The polymer beads could be exfoliated to yield many spherical particles dispersed in the resulting polyethylene particles during ethylene polymerization. The influence of the polymer beads on the catalytic behavior of the supported catalyst and morphology of the resulting polyethylene was investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 873–880, 2003