Calorimetric investigation of polymerization reactions. IV. Curing reaction of polyester fumarate with styrene

The curing reaction of polyester fumarate with styrene was investigated with a differential scanning calorimeter (DSC) operated isothermally. The change in rate of cure was followed over the whole range of conversion. The rate of cure is accelerated by the gel effect to about ten to fifty times the rate of model copolymerization of diethyl fumarate with styrene. This autoacceleration is much enhanced for systems with higher crosslinking densities and at lower temperatures. The results confirm that both termination and propagation steps of the curing reaction are controlled by diffusion of polymeric segments and monomer molecules over almost the whole range of conversion. The final extent of conversion is short of completion for isothermal cure and even for postcure of polyester fumarate with styrene because of crosslink formation. The final conversion of isothermal cure decreases with increasing crosslinking density and shows a maximum with increasing reaction temperature. This temperature dependency of the final conversion is caused by the difference in the activation energies for two propagation rate constants k_pf and k_ps, which were evaluated to be 7–10 and 5–8 kcal/mole, respectively, for the intermediate stage of the curing reaction.     

γ Radiolysis of polyethylene grafted with styrene

γ Radiolysis of polyethylene grafted with styrene of 0–76 wt % was carried out at 30–100°C in vacuo with a dose rate of 6.35 × 10⁵ rad/hr. The formation of hydrogen and trans-vinylene unsaturation decreased as the content of styrene unit in polymer increased and the rate of formation was described by zero-order formation kinetics with respect to each concentration combined with first-order disappearance. The gel fraction changed with the content of styrene unit according to irradiation time and temperature. The gel data were evaluated by using the Charlesby–Pinner equation. Kinetic analysis showed that in γ radiolysis of polyethylene grafted with styrene the formation of hydrogen is somewhat retarded, the crosslinking and main chain scission are accelerated, and the disappearance of hydrogen and formation and disappearance of trans-vinylene unsaturation are almost entirely unaffected. On the basis of these results the reactions induced by γ rays in graft polymer were discussed in connection with the reaction mechanisms of the γ radiolyses of polyethylene and polystyrene.     

Investigation of Conversion of Styrene and Fumarate Double Bonds in Unsaturated Polyester Resins

The conversion of styrene and fumarate double bonds in the copolymerization of unsaturated polyesters and styrene was investigated. Several commercial polyester resins including Bisphenol-type, Iso-type and G-type resins were used. The initial fumarate double bond, the equivalent double bond per 100 g of the polyesters, was determined by the hydrogenation procedure which was developed for the present study. Using palladium-carbon catalyst and benzene-acetone (1:1) mixture, polyester resin can be hydrogenated satisfactorily.

The cured resin was extracted with chloroform. The styrene in the chloroform was determined by ASTM D-1159, bromine index method. The conversion of the fumarate double bond was calculated from the soluble part of polyester resin using the theoretical equations which were derived from the basic theory of Flory. The validity of the equations was examined by application of Funke et al.'s experimental results and found to be satisfactory. With the confidence of these results, commercial polyester resins were investigated to determine the effect of the condition of polymerization on the conversion of styrene and fumarate double bonds.

For all the polyesters the conversion of styrene was at least over 80% after a room temperature cure of 24 hr with a dimethyl anilin-cobalt naphthenate-methyl ethyl ketone peroxide three component catalyst system, and it reached approximately 100% after postcure of 100[ddot]C for 2 hr. On the other hand, the conversion of the fumarate double bond depended greatly upon the type of the resin. Bisphenol-type resin gave the highest conversion, and the conversion for Iso-type resin was higher than that for G-type resin. In the case of Bisphenol-type resin, there was no difference in the conversion of fumarate double bond between the room temperature cure and the postcure, but the conversions of fumarate double bond for G- and Iso-type resins were increased remarkably by postcure. The Barcol hardness is applicable to determine the conversion of styrene for the specified polyesters based on the relationship between the conversion of styrene and the Barcol hardness.     

Morphology and performance of unsaturated polyester nanocomposites modified with organoclay and thermoplastic polyurethane

<正>Unsaturated polyester(UPR)/thermoplastic polyurethane(TPU)/organoclay nanocomposites were prepared by melt compounding of thermoplastic polyurethane and unsaturated polyester prepolymer,and then mixing with the hybrids of styrene monomers and organoclay at ambient temperature.The crosslinking reaction eventually occurred through the unsaturated polyester prepolymer and styrene monomer.The morphology of the composites was investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that the impact strength of UPR/TPU/organoclay nanocomposites increases obviously;the cure shrinkage decreases markedly,the glass transition temperature is enhanced and an elastic response to the deformation is prominent at the temperature above 10℃.     

Effects of copolymer composition on the formation of ionic species,hydrogen evolution,and free-radical reaction in γ-irradiated styrene-butadiene random and block copolymers

Block and random copolymers of butadiene and styrene as well as polybutadiene and polystyrene homopolymers have been investigated with respect to formation of trapped electrons, contribution of ionic species to crosslinking, and hydrogen gas evolution due to γ radiation. The decay kinetics of the disubstituted benzyl radical has also been studied. The yields of electron trapping G(e^?) are measured. The G(e^?) increase linearly with increased polystyrene content in block polymers, while in random copolymer a deviation from a linear relation is observed. The contribution of ionic reactions to crosslinking is about 25–35% of the total crosslinking yield. Hydrogen production in block copolymers is approximately a linear function of the weight-fraction additivity of the yield of hydrogen formation in polystyrene and polybutadiene homopolymers. Energy transfer from butadiene units to styrene units in random copolymers resulted in a deviation from such an additivity relation. The decay of the disubstituted benzyl free radical in block copolymers is a second-order reaction. In random copolymer, the decay is best interpreted in terms of equation based on a second-order decay mechanism of a fraction of the free radicals decaying in the presence of other nondecaying free radicals.     

Spectroscopic Study of Di-Imide Hydrogenation of Natural Rubber

The diimide hydrogenation of natural rubber (NR) was studied by using p-toluenesulfonylhydrazide (TSH) as a diimide-releasing agent. The microstructure and the percentage of hydrogenation were studied by Raman, ¹H-NMR and ¹³C-NMR spectroscopic techniques. Quantitative measurements on fraction of hydrogenated part gave the results in good agreement by using these techniques. The results indicated that percent hydrogenation increased with increasing of reaction time and about 80-85 % hydrogenation was achieved when a two-fold excess of TSH was used. The vibrational characteristic of C=C bond of NR is strongly Raman active and noted at 1663 cm⁻¹. The decrease of this signal was clearly observed during the progress of hydrogenation but the vibrational frequency of the cis and trans structures of the trisubstituted olefin unit of NR can not be differentiated by this technique. While ¹H- and ¹³C-NMR analysis showed that cis-trans isomerization of carbon-carbon unsaturation of NR occurred during hydrogenation.     

Kinetics and mechanism of Rh(III) catalyzed oxidation of styrene,stilbene and phenylacetylene by acid periodate

The kinetics of Rh(III) catalyzed oxidative cleavage of styrene, stilbene, and phenylacetylene by periodate have been investigated in the presence of HClO₄ in aqueous acetic acid medium. The kinetic orders are completely dependent on the nature of unsaturation. In the cases of styrene and stilbene the reactions are first order in the oxidant and Rh(III), zero order with respect to the substrate, and independent of [H⁺], whereas in the case of phenyl acetylene the reaction is zero order with respect to the oxidant and first order with respect to the substrate and Rh(III). The reaction is independent of [H⁺] in the range of 0.01?0.05M studied. A mechanism involving higher Rh(V) species has been postulated in the case of styrene as well as stilbene, and metal ion catalyzed hydration has been postulated in case of phenylacetylene. The influence of the solvent has been investigated, and a comparative analysis of the kinetic orders of styrene and stilbene is made with those of phenylacetylene.     

The introduction of hydroxyl functionality into polymers: The synthesis,polymerization, and hydrolysis of vinylbenzyl acetate

Vinylbenzyl acetate was synthesized in yields greater than 80% via the reaction of vinylbenzyl chloride with potassium acetate. Radical copolymerization of the monomer with styrene and methylmethacrylate were studied at 60°C. Reactivity ratios determined from FT-IR analysis of low conversion copolymerizations with styrene (M₁) were r₁ = 0.78 ± 0.07 and r₂ = 1.33 ± 0.13. Polymers and copolymers of vinylbenzyl acetate were found to completely hydrolyze in dioxane/water/base solution to yield hydroxymethyl functionality. Size exclusion chromatography studies indicated that the hydrolysis proceeded without crosslinking. This procedure is a useful method for the introduction of hydroxyl functionality on polymers and avoids crosslinking problems common in previously reported methods.     

Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts

Anionic graft copolymers were synthesized through grafting of poly(ethylene glycol) monomethyl ether (MPEG) onto terpolymers containing succicinic anhydride groups. The backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene, and one of the following monomers: methyl methacrylate, ethylhexyl methacrylate, and diethyl fumarate. MPEG of different molecular weights were grafted onto the backbone through reactions with the cyclic anhydride groups. In this reaction one carboxylic acid group is formed together with each ester bond. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and ¹H-NMR. Thermal properties were examined by DSC. Graft copolymers containing 50% w/w of MPEG 2000 grafts were found to be almost completely amorphous, presumably because of crosslinking, and hydrogen bonding between carboxylic acid groups in the backbone and the ether oxygens in MPEG grafts. © 1995 John Wiley & Sons, Inc.     

Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n‐butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free‐radical process. Although the polyester‐core‐based RAFT agent mediated polymerization of n‐butyl acrylate displayed a linear evolution of the number‐average molecular weight (M_n) up to high monomer conversions (>70%) and molecular weights [M_n > 140,000 g mol^?1, linear poly(methyl methacrylate) equivalents)], the corresponding styrene‐based system reached a maximum molecular weight at low conversions (≈30%, M_n = 45,500 g mol^?1, linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n‐butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene‐based star polymers were successfully cast into highly regular honeycomb‐structured microarrays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3847–3861, 2003     

Lipase-Catalyzed Polyester Synthesis

Abstract

The use of lipase as biocatalyst in polyesterification of aliphatic diacids or their derivatives, and diols in an organic solvent has been discussed. We have demonstrated that bis(2-chloroethyl) esters of succinic, fumaric, and maleic acid, and bis(2,2,2-trifluoroethyl) sebacate and -dodecanedioate can be polymerized by lipase-catalyzed polytransesterification. Maleate was isomerized to fumarate even under mild reaction conditions, resulting in poly(1,4-butyl fumarate). In order to obtain a high mass-average molar mass of the polyester, solid Mucor miehei lipase was found to be the best lipase and diphenyl ether the best solvent of several investigated. There was no clear relationship with the log P value of the solvent and the polyesterification activity of lipase. The highest degree of polymerization (DP = 184) of poly(1,4-butyl sebacate) with a mass-average molar mass of 46,600 g·mol^?1 was obtained in polytransesterification of bis(2,2,2-trifluoroethyl) sebacate and 1,4-butanediol using a programmed vacuum profile. However, a mass-average molar mass as high as about 42,000 g·mol^?1 (DP = 167) was also obtained with free sebacic acid when vacuum was employed to remove the water formed during esterification. The mass average molar mass of the polyester increased with an increase in the relative quantity of lipase up to 1 g per 1.5 mmol of diacid, with an increase in the molar mass of the aliphatic diol up to 1,5-pentanediol, and with an increase in the concentration of substrates up to 0.83 M.     

Anionic copolymerization of [60]fullerene with styrene initiated by sodium naphthalene

The novel C₆₀–styrene copolymers with different C₆₀ contents were prepared in sodium naphthalene-initiated anionic polymerization reactions. Like the pure polystyrene, these copolymers exhibited the high solvency in many common organic solvents, even for the copolymer with high C₆₀ content. In the polymerization process of C₆₀ with styrene an important side reaction, i.e., reaction of C₆₀ with sodium naphthalene, would occur simultaneously, whereas crosslinking reaction may be negligible. ¹³C-NMR results provided an evidence that C₆₀ was incorporated covalently into the polystyrene backbone. In contrast to pure polystyrene, the TGA spectrum of copolymer containing ∼ 13% of C₆₀ shows two plateaus. The polystyrene chain segment in copolymer decomposed first at 300–400°C. Then the fullerene units reptured from the corresponding polystyrene fragments attached directly to the C₆₀ cores at 500–638°C. XRD evidence indicates that the degree of order of polymers increases with the fullerene content increased in terms of crystallography. Incorporation of C₆₀ into polystyrene results in the formation of new crystal gratings or crystallization phases. In addition, it was also found that [60]fullerene and its polyanion salts [C₆₀ⁿ⁻(M⁺)_n, M = Li, Na] cannot be used to initiate the anionic polymerization of some monomers such as acrylonitrile and styrene, etc.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2653–2663, 1998     

Radiation-induced polymerization at high dose rate. V. Butadiene in bulk

Bulk butadiene was polymerized by a cationic mechanism in a wide dose rate range. The M?_n of the product was about 2300, independent of dose rate. The polymer had 83% residual unsaturation and the remaining double bond was 77% trans and 23% vinyl and had no cis unit. When the polymer yield exceeded 10% gel was formed, but the value of the residual unsaturation in the polymer remained unchanged. This indicated a mechanism that correlated propagation, cyclization, and crosslinking reactions with a cationic intermediate.     

Kinetics of crosslinking reactions. 1. Reaction rate of intramolecular crosslinkings by using a soluble microgel

Soluble microgels with several pendant vinyl groups were synthesized by radical copolymerization of methyl methacrylate (MMA) with p-divinyl benzene (p-DVB). The polymerization conditions used for intramolecular crosslinking of microgels were chosen from gel permeation chromatograph (GPC) measurements of the reaction products. The rate constant of intramolecular crosslinking (k_pⁱ) was estimated from the changes in the concentration of pendant vinyl groups of microgel by using photometrical measurements at 30°C assuming a unimolecular termination mechanism of polymer radicals. As a result, k_pⁱ showed larger values than k_p of styrene and depended strongly on the internal structure of the microgels.     

Effect of substituents in the styrene ring on the dynamic mechanical relaxations of a styrene-crosslinked unsaturated polyester resin

The dynamic mechanical properties of a series of polyester resins made from a maleic/phthalic anhydride-based unsaturated polyester crosslinked with each of styrene, 4-methyl styrene, 4-ethyl styrene, 4-n-butyl styrene, 4-isopropyl styrene, tertiary butyl styrene, 4-chlorostyrene, and 3,4-dichlorostyrene were studied. The order of the α transition temperatures was as expected from that for the homopolymers, except in the case of the chlorostyrenes, for which dipolar interactions with the polyester chain may be important. The styrene bridges appeared to be involved in a steric interaction (and in the case of the chlorostyrenes, a dipolar interaction) with the β relaxing ester species. It is suggested that both the γ and γ′ relaxations involve similar interactions between the matrix and the relaxing moieties. For the 4-n-butyl styrene resin, an additional relaxation below ?170°C was observed, and is ascribed to relaxation of the n-butyl group.     

Effects of electron beam preirradiation on the γ radiolysis of polyethylene

The γ radiolysis of polyethylene preirradiated with electron beams to 3 Mrad was carried out at 30–100°C in vacuo with a dose rate of 6.35 × 10⁵ rad/hr. The hydrogen formation in the γ radiolysis was little affected by the preirradiation of electron beams, whereas the formation of trans-vinylene unsaturation and gel was somewhat retarded. The rates of the formation of hydrogen and trans-vinylene unsaturation were described by the zero-order formation kinetics with respect to each concentration combined with the first-order disappearance. The apparent rate constants and activation energies for the formation and disappearance of hydrogen and trans-vinylene unsaturation were almost independent of the preirradiation. The gel fraction was analyzed by using the Charlesby–Pinner equation. The G values of crosslinking and main chain scission were increased by the preirradiation, whereas their activation energies remained unaltered. On the basis of these results the effects of preirradiation on the reactions induced by γ rays in polyethylene were discussed.     

Chain extension of polyesters PET and PBT with N,N′-bis (glycidyl ester) pyromellitimides. I

Three N,N′-bis (glycidyl ester imide) of pyromellitic acid (diepoxides) were prepared and were used as chain extenders for poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). The typical reaction conditions for the coupling of the polyester macromolecules were heating with the chain extender under argon atmosphere above the melting temperature (280°C for PET and 250°C for PBT) for several minutes. The Characterization of the samples, obtained at variable residence times in the reactor, was based on solution viscosity measurements and carboxyl and hydroxyl end-group determinations. Two of the diepoxides used gave satisfactory results. Starting from a PET having intrinsic viscosity [η] = 0.60 dL/g, and carboxyl content CC = 42 eq/10⁶ g, one could obtain PET with [η] = 1.15 dL/g and CC = 16 eq/10⁶ g within 30 min at 280°C. Analogous results were observed for PBT. The hydroxyl content of polyester in all cases was increased. When the quantity of the chain extender used was higher than that theoretically required for its reaction with all carboxyl end groups of the polyester, this resulted in some gel formation indicative of crosslinking. © 1995 John Wiley & Sons, Inc.     

Poly(styrene peroxide) and Poly(methyl methacrylate peroxide) for Grafting on Unsaturated Bacterial Polyesters

A new soluble terephthaloyl oligoperoxide (OTP) was synthesized by the reaction of terephthaloyl peroxide and 2,5‐dimethyl 2,5‐dihydroperoxy hexane. Thermal polymerization of vinyl monomers (styrene, methyl methacrylate) with OTP yielded poly(styrene peroxide) (PS‐P) and poly(methyl methacrylate peroxide) (PMMA‐P) which are used in the grafting reactions onto medium chain length unsaturated bacterial polyester obtained from soybean oily acids with Pseudomonas oleovorans poly(3‐hydroxy alkanoate), (PHA). PS‐g‐PHA and PMMA‐g‐PHA graft copolymers isolated from related homopolymers were characterizated by ¹H NMR spectrometry, FT‐IR spectroscopy, thermal analysis and gel permeation chromatographic (GPC) techniques. Swelling measurement of the crosslinked graft copolymers were also measured to calculate q_v values.     

Kinetic study of the γ radiolysis of polyethylene

A kinetic study was made of the formation of hydrogen and trans-vinylene unsaturation in the radiolysis of polyethylene induced by γ rays with a dose rate of 6.35 × 10⁵ rad/hr at 30–100°C in vacuo. The rates of the formation of hydrogen and trans-vinylene unsaturation were described by the zero-order formation kinetics with respect to each concentration combined with the first-order disappearance. The apparent rate constant for the formation of hydrogen increased gradually with rising irradiation temperature to give the activation energy of 0.6 kcal/mole. On the other hand, those for the disappearance of hydrogen and the formation and disappearance of trans-vinylene unsaturation were almost independent of temperature. The G values for crosslinking and main-chain scission were obtained from the gel data by using the Charlesby-Pinner equation, and the activation energy of 1.5 kcal/mole was given for both of them. On the basis of these results the reactions induced by γ rays in solid polyethylene were discussed.     

Biobased vinyl levulinate as styrene replacement for unsaturated polyester resins

Vinyl levulinate (VL) is used as a biobased reactive diluent in styrene (St)‐free unsaturated polyester resins (UPR). The reactivity ratios for the radical copolymerization of VL with diethyl fumarate (DEF) are determined by the Jaacks method (r_VL = 0.01 and r_DEF = 0.81 at 60 °C in DMSO‐d₆). The properties of UPRs having a stoichiometric ratio between unsaturated groups from the UPR and either St or VL are compared. Defect‐free, slightly yellow, transparent, and rigid thermosets are obtained after a mild curing cycle. Due to unfavorable reactivity ratios about 5.5 wt % of unpolymerized VL remains inside the network and acts as plasticizer. Consequently, compared with St‐based ones, VL‐based UPRs exhibit lower α relaxation (T_α = 180 and 100 °C, respectively), lower elastic moduli at the rubbery plateau (G′ = 10⁸ and 10⁷ Pa) and lower mechanical properties as measured by three points bending tests. Strain at break (ε_f = 1.8 ± 0.2%) and Charpy impact strength (～2.7 ± 0.3 kJ m^?2) are comparable independently of the RD chemical nature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3356–3364