Duane B. Priddy

Spontaneous polymerization of styrene in the presence of acid: further confirmation of the Mayo mechanism

Abstract Flory and Mayo have proposed alternative mechanisms to explain the spontaneous polymerization of styrene. Both involve the formation of reactive styrene dimers capable of generating initiating radicals. However, the dimer intermediate proposed in the Mayo mechanism has defied all attempts at isolation. Since the Flory dimer would be expected to be stable to acid while the Mayo dimer would not, spontaneous styrene polymerization was studied in an acid environment to determine the effects on oligomer structure, polymerization rate, and polymer molecular weight. The results clearly show that the initiating Mayo dimer is deactivated by acid, forming high levels of inactive dimer. The decreased initiation results in a lower concentration of growing polymer chains, subsequently lowering the rate of termination (by chain coupling). The end result is a large shift of the spontaneous rate-molecular weight relation for polystyrene.

Nitroxide‐mediated styrene polymerization initiated by an oxoaminium chloride

ABSTRACT: An oxoaminium chloride that is prepared by reacting 2,2,6,6-tetrameth-ylpiperidinyl-1-oxy (TEMPO) with chlorine in carbon tetrachloride initiates radicalpolymerization of styrene at 120°C. In the early stages of polymerization, a monomericadduct, 2,2,6,6-tetramethyl-1-(2-chloro-1-phenylethoxy)piperidine, is formed. Thereaf-ter, styrene polymerization exhibiting the characteristics of living polymerization pro-ceeds. High molecular weight polymers with relatively narrow molecular weight dis-tributions are obtained by this polymerization. 1 H-NMR spectra of the polymers revealthat a chlorine atom and a TEMPO group are present at the a- and v-termini,respectively. The monomeric adduct was prepared by heating the oxoaminium chlorideand styrene in carbon tetrachloride at 65–70°C, and was characterized by 1 H- and 13 C-NMR spectroscopy. It was found to be suitable as an initiator for nitroxide-medi-ated radical polymerization of styrene to make polymers with chlorine on the chain end.

Photo-degradable polystyrene Part II: styrene-co-vinyl ketones

Styrene was copolymerized with two commercially available ketone functional monomers; i.e., methyl vinyl ketone (MVK) and benzalacetone (BA). BA copolymerizes poorly with styrene. This, along with its low volatility, results in high residual BA monomer in the final polymer. 13C NMR characterization of SBA showed that the polystyryl radical adds to both carbons of the double bond and at similar rates. The SMVK copolymers were found to degrade twice as efficiently as SBA copolymers.

Photo-degradable polystyrene Part I: enhancing the photo-degradability of polystyrene by the addition of photosensitizers

Abstract This paper is the first in a series which investigates options for enhancing the photo-degradability of polystyrene. This paper specifically focuses on the accelerated rate of photo-degradation of polystyrene film and foam achievable by the addition of benzophenone and benzoin. The results show that both benzophenone and benzoin accelerate the rate of photo-degradation of polystyrene films at approximately the same rate when compared at the same weight loading (0·5% w/w). However, in foam samples, benzophenone is more effective.

Development of continuous anionic styrene polymerization technology

ABSTRACTAnionic polymerization is not used commercially to manufacture any styrene containing polymers, except for block copolymers. This is due to technical problems (eg. feed purification) associated with anionic chemistry. Since anionic polymerization offers several potential product and process advantages over free radical polymerization, solutions to these technical problems were developed utilizing continuous reactor designs and conditions typical of current commercial free radical polymerization processes. Styrene was anionically polymerized in 50-60% w/w ethylbenzene solvent at high temperature (90-100°C) in a well-mixed CSTR to produce high quality polystyrene at over 99% conversion of styrene monomer and having a polydispersity of 2.0 to 2.2. Polystyrene with a polydispersity as low as 1.7 was produced utilizing a slowly recirculated, stratified agitated tower reactor.

Polymerization and copolymerization of dimethyl(1-ethoxycarbonyl)vinyl phosphate

Abstract Dimethyl(1-ethoxycarbonyl)vinyl phosphate (DMEVP), prepared in nearly quantitative yield from the reaction of ethyl bromopyruvate with trimethyl phosphite, polymerizes easily by free radical initiated polymerization and copolymerizes readily with styrene (S). Reactivity ratios determined at 60 and 135 °C were r S =0.21±0.02, r DMEVP =0.35±0.05 and r S =0.31±0.03, r DMEVP =0.31±0.04, respectively. Glass transition temperatures and thermal stabilities of the copolymers decreased but char yields obtained upon thermolysis increased as the DMEVP contents of the copolymers increased. 1 H, 13 C and 31 P NMR spectra of the copolymers are reported. DMEVP exhibited mild chain transfer activity ( C tr ∼0.01) in styrene polymerizations conducted at 135 °C and in emulsion polymerizations at 50 °C.

Approaches to branched polystyrene using bulk free-radical polymerization

Preparation of branched polystyrene using continuous bulk styrene polymerization is extremely difficult due to gel formation and can even lead to reactor plugging. This investigation explores the concept of post-polymerizer branching by placing latent functional groups along the polymer backbone which couple during high-temperature devolatilization of the polymerizer effluent. The latent functional monomer pair investigated is glycidyl methacrylate and acrylic acid. The key to producing a branched polystyrene that is thermally stable is to add one of the latent functional monomers in large excess, making the other monomer the limiting reagent.

Photo-degradable polystyrene Part IV: comparison of photo-degradation efficiency of random styrene-co-vinyl ketones (SVK) versus blends of polystyrene and SVK concentrates

Abstract Random vinyl ketone copolymers were found to degraded more efficiently than blends of polystyrene with vinyl ketone copolymer concentrates containing the same molar ketone content. The blends were prepared from polystyrene and styrene-co-methyl vinyl ketone (SMVK) resins containing from 0·25–10 mol% ketone or ECOLYTE™ polystyrene. Foam food packages and films were prepared as test specimens for this study. Both outdoor (Southern Florida) and indoor (QUV) weathering test were conducted.

Photo-degradable polystyrene part III: Preparation of photo-degradable styrene-co-vinyl ketones via in-situ dehydrative monomer generation from β-hydroxyketones

Abstract This paper focuses on the preparation, characterization, and photo-degradation of styrene-co-vinyl ketones prepared by the dehydrative copolymerizations of β-hydroxy ketones with styrene. Specifically, 1-hydroxy-2-methylpentan-3-one and 4-hydroxybutan-2-one were copolymerized with styrene in sealed ampoules in the presence of an acid catalyst. The dehydrative polymerization technique afforded copolymers that were analogous to those obtained from direct copolymerization of styrene with the respective vinyl ketones. The copolymers were isolated and characterized using FTIR, 13 C NMR, and gel permeation chromatography (GPC) analyses. Films cast from methylene chloride solutions of the copolymers were irradiated in a weatherometer and molecular weight changes monitored by GPC.