Chemistry of novolac resins. II. Reaction of model phenols with hexamethylenetetramine

It is proposed that the reactions of hexamethylenetetramine (HMTA) with 2,4-xylenol and with 2,6-xylenol occur by different pathways. The rate of reaction and the final product distribution depend on the initial xylenol : HMTA ratio and are different in the two systems. Measured by HMTA consumption, with 2,4-xylenol the reaction rate increased with increasing xylenol : HMTA ratios, whereas with 2,6-xylenol the rate of reaction decreased with increasing 2,6-xylenol : HMTA ratio. In systems which contain both 2,4- and 2,6-xylenol, a strong preference for reaction of the HMTA with the ortho site of 2,4-xylenol was noted. This preference was apparent even in mixtures in which 2,6-xylenol was present in greater amounts than 2,4-xylenol. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1389–1398, 1997     

Macrocyclic oligoimides. I. Preparation of macrocyclic oligoetherimides via Kricheldorf substitution polymerization

Macrocyclic oligoetherimides were synthesized by means of Kricheldorf's nucleophilic aromatic substitution polycondensation. A solution containing equimolar quantities of bis(trimethylsilyl ether) of bisphenol and arylenebis(fluorophthalimide) was continuously added into a high boiling solvent containing CsF catalyst under a pseudo-high dilution condition. The resulting reaction mixture contained a high yield of cyclic oligomers which could be isolated by solvent extraction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 759–767, 1997     

Polymer-supported reagents. II. Kinetics of esterification of acrylic acid with n-butanol using polymer supported titanium tetrachloride as catalyst

Crosslinked poly(4-vinylpyridine-co-styrene) was prepared and functionalized with titanium tetrachloride to afford the corresponding poly(4-vinylpyridine-co-styrene)-titanium tetrachloride complex. This insoluble functionalized polymer-supported catalyst shows good catalytic activity for esterification reactions. In this article, the kinetics of esterification of acrylic acid with n-butanol is reported. The rate of formation of product depends on many experimental parameters, viz., stirring speed, concentration of acrylic acid, catalyst amount, temperature, percent active site, percent crosslinking, and mesh size of the polymer catalyst. The reaction rates were found to increase with increase in the stirring speed, concentration of acrylic acid, catalyst amount, and temperature, and decreases with increasing percentage crosslinking and mesh size of the polymer beads. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 727–733, 1997     

Reactive surfactants in heterophase polymerization. VIII. Emulsion polymerization of alkyl sulfopropyl maleate polymerizable surfactants (surfmers) with styrene

The copolymerization of styrene with two polymerizable surfactants (surfmers) based on maleic acid (dodecyl sodium sulfopropyl maleate and tetradecyl sodium sulfopropyl maleate) was studied in batch emulsion polymerizations. The surfmer conversion was obtained by serum replacement with water and subsequent analysis of the recovered, unreacted surfmers with two-phase titration. It was found that both surfmers copolymerized well with styrene and their partial conversion was higher than that of styrene. These results are contradictory to what was found before in the literature using ultrafiltration with methanol, and the differences are explained on the basis of oligomer formation: The oligomers formed are detected if the latices are washed with methanol. It was found that at the end of the polymerization (almost complete conversion of both styrene and surfmer) only 45% of the surfmer groups were present on the particle surface, which is in agreement with a high conversion of the surfmer at the beginning of the reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2561–2568, 1997     

Transition metal-catalyzed tandem isomerization and cationic polymerization of allyl ethers. II. Structural and mechanistic studies

In the presence of organosilanes, dicobalt octacarbonyl catalyzes the polymerization of alkyl allyl ethers to give high molecular weight polymers. This article reports the results of a detailed mechanistic study of this new polymerization reaction. The evidence obtained in this study supports a stepwise process involving first, the reaction of dicobalt octacarbonyl with an organosilane to form HCo(CO)₄ and R₃SiCo(CO)₄. In subsequent steps, HCo(CO)₄ isomerizes the allyl ether to a 1-propenyl ether and then this compound is polymerized by the formal transfer of a silyl cation from R₃SiCo(CO)₄. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1985–1997, 1997     

Kinetic study of gas phase olefin polymerization with a TiCl4/MgCl2 catalyst I. Effect of polymerization conditions

This study focuses on the kinetics of ethylene/propylene (homo/co) polymerization reactions using a high activity TiCl₄/MgCl₂/AlEt₃ catalyst. The reactor system is a gas phase reactor equipped with an on-line composition control scheme. As such, important kinetic data such as the instantaneous reaction rate of each monomer is readily obtained. In the investigation, experiments are performed to study the effects of comonomer composition variations, temperature variations, hydrogen concentration variations, and variations in the Al/Ti ratio. It is observed that the ethylene and propylene instantaneous reaction rates show a rather peculiar pattern with the appearance of a second peak. Our work linked the existence of this peak to the Al/Ti ratio used. A theory based on the oxidation state change is proposed. This theory is also used to explain the effects of temperature changes and hydrogen concentration changes on the system. A variety of analytical techniques are employed to study the polymer properties and evidence is provided to support the existence of polymer partial melting at relatively high reaction temperatures. The resulting diffusion limitation is believed to be partially responsible for the observed activity decrease at such elevated temperatures. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2063–2074, 1997     

ESR study on chemical crosslinking reaction mechanisms of polyethylene using a chemical agent—II. The effect of phenolic antioxidants

The effect of antioxidant on the reaction mechanism of chemical crosslinking of polyethylene (PE) with dicumyl peroxide (DCP) at high temperatures was investigated by electron spin resonance (ESR). The antioxidant reacts with the alkyl radicals in PE formed by the thermal decomposition of DCP above 120°C, and disturbs the crosslinking. A phenolic type antioxidant produced the phenoxy radical by the reaction with alkyl radicals formed in PE. It is suggested that the selection of a suitable antioxidant for PE crosslinking can be made by ESR analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2431–2439, 1997     

Multidimensional benzobisoxazole rigid-rod polymers. I. Preparation and characterization

Two- and three-dimensional rigid-rod polymers containing benzobisoxazole structures were prepared through the polycondensation in polyphosphoric acid of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with trimesic acid and 1,3,5,7-tetrakis(4-carboxylatophenyl)adamantane, respectively. Thermal properties of the polymers were determined by differential scanning calorimetry, thermogravimetric/mass spectral analysis, and isothermal aging studies. The multidimensional polymers exhibited lower solution viscosities and lower thermooxidative stabilities than the one-dimensional polymer generated by the homopolymerization of ABA under identical reaction conditions. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3451–3456, 1997     

A kinetic study of the formation of polystyrene stars using 1,2-bis(trichlorosilyl)ethane

The kinetics of formation of a chlorosilane-linked polystyrene six-arm star is reported. The precursor arm material (M_n = 88,000) was made using anionic polymerization in benzene. Prior to addition to the 1,2-bis(trichlorosilyl) ethane linking agent, the anions were endcapped with about five units of isoprene. Size exclusion chromatography using multiangle laser light scattering and viscosity detectors was utilized for characterization. This technique has allowed the molecular weights, radii of gyration, and intrinsic viscosities to be measured for star components in aliquots taken from the reactor at various times. It was found that four-arm star is formed within 30 min after the addition of the chlorosilane linking agent. There is a linear relationship between the logarithm of molecular weight of the star samples and logarithm of time of the reaction after the formation of the four-arm star. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 587–594, 1997     

Anionic ring-opening polymerization behavior of a seven-membered cyclic carbonate; 1, 3-dioxepan-2-one

Anionic ring-opening polymerization of a seven-membered cyclic carbonate, 1,3-dioxepan-2-one ( 1 ), was carried out to observe that the higher the polymerization temperature and lower the initial monomer concentration were, the lower the yield and molecular weight, and wider the molecular weight distribution of the obtained polymers were. The back-biting reaction and the formation of cyclic oligomers of 1 were observed during the polymerization of 1 . The relative polymerization rate of 1 was about 35 times faster than that of six-membered carbonate, 1,3-dioxan-2-one ( 3 ). The ΔHps of 1 and 3 estimated by MO (PM3) calculations were −9.8 and −4.4 kcal/mol, respectively. 1 could easily undergo the ring-opening polymerization based on larger ring strain. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1375–1380, 1997     

Phase separation in segmented poly(urethane urea) copolymers during reaction injection molding (RIM) polymerization

In situ experiments were performed with a portable RIM (reaction injection molding) minimachine interfaced to an FTIR spectrophotometer to follow the reaction chemistry and monitor phase separation of copoly(urethane urea)s during RIM polymerization. The PUU copolymers were based on ethylene oxide-capped poly(propylene oxide) polyether diol, 3,5-diethyltoluenediamine (DETDA), and uretonimine liquefied 4,4′-diphenylmethane diisocyanate. The effect of catalyst concentration on the degree of phase separation in the as-molded RIM PUU copolymers was investigated by using differential scanning calorimetery and scanning electron microscopy as supplementary methods. The results suggested that an increase of degree of phase separation and a decrease of the size of hard-segment-rich domains take place with a rise of catalyst concentration. The morphological feature was a consequence in combination with the increase in relative rate of urethane formation and the ordering of hydrogen bonding through urea groups. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 865–873, 1997.     

Copolymerization of bis(2-oxazoline)s,anhydrides, and diols or diamines. Reaction mechanisms and polymer properties

The preparation of linear poly(ester-amide)s from monoanhydrides, bis(2-oxazoline)s (namely 2,2′-(1,4-phenylene)bis(2-oxazoline)) and a third comonomer is discussed. The polymerization reactions were carried out in bulk between 150 and 200°C. When the third monomer is a diol, poly(ester-ester-amide)s are obtained. Diols of different structure were used: α,ω-diols having up to 12 carbon atoms, ethylene glycol oligomers (two or three repeating units), cyclic diols, etc.; glutaric, 3,3-dimethylglutaric and maleic anhydrides were used as monoanhydrides. The polymers were studied from the point of view of thermal properties, finding a substantial agreement between the structure of the monomers and the glass transition temperature of the polymers. By using primary diamines as a third comonomer, the reaction does not lead to the formation of a polymeric product. The failure of the polymerization was attributed to a competitive reaction that prevents the polymerization. After the amine group has reacted with the anhydride, cyclization of the so-formed carboxyalkylamide occurs, giving an imide derivative, unable to react further. Therefore, only a mixture of low molecular weight compounds is obtained in this case. When the diamine is secondary, the imidization reaction is not possible, and linear poly(amide-ester-amide)s are obtained. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3241–3248, 1997     

Effects of liquid crystalline structure formation on the curing kinetics of an epoxy resin

The curing kinetics of a system containing 4,4′-diglycidyloxy-α-methylstilbene (DOMS) and different functionality amines, N-ethylaniline (NEA), aniline, benzenesulfonamide (BSA), and sulfanilamide (SAA), have been studied by differential scanning calorimetry (DSC) under isothermal conditions. The phase transformations during curing of the systems have been monitored by a crosspolarized optical microscope equipped with a hot-stage and photo detector. It has been found that the growth of a nematic liquid crystal structure does not cause a discrepancy from the autocatalytic model for the reactions between aniline and epoxy. There is no liquid crystalline structure formed for the systems containing NEA or BSA, which follow the autocatalytic kinetic models within the temperature range of 120–150°C. For the curing reactions between DOMS and SAA, there is a big deviation from the autocatalytic model when the liquid crystals transfer from a nematic structure to a smectic structure. Unlike the usual decrease of reaction rate resulting from diffusion in a heterogeneous reaction, the reaction rate is enhanced. A modified kinetic model has been constructed for this reaction system by introducing a pseudoconcentration term caused from the liquid crystalline structure formation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1105–1124, 1997     

Study on ketalization reaction of poly(vinyl alcohol) by ketones. IX. Kinetic study on acetalization and ketalization reaction of 1,3-butanediol as a model compound for poly(vinyl alcohol)

A kinetic study was carried out on the acetalization reaction of 1,3-butanediol, as a model compound for poly(vinyl alcohol) (PVA), in water, under acidic conditions. Since these equilibrium constants of ketalization reaction of 1,3-butanediol and ethylene glycol are so small, the kinetic parameters were estimated from the hydrolysis reactions of the corresponding ketals. It was made clear that these reactions proceed in the reversible bimolecular reaction, and the heat of reaction and activation energy are nearly equal to that of PVA. The rate constants of hydrolysis reaction (k′s) of model compounds were calculated on the basis of value of acetone ketal, Hammett-Taft's equation log k′s/k′so – 0.54(n – 6) = ρ^*σ^* was established, and the value of ρ^* was obtained (3.60), which coincided with the value of PVA. Therefore, it was made clear that the hydrolysis reactions of acetals and ketals are electrophilic reaction (SE II reaction) and the step of rate determination is the formation of hemiacetal and hemiketal. The rate constants of hydrolysis reaction of 1,3-butanediol acetals and ketals were approximately 10–20 larger, and those of ethylene glycol were approximetly 50–80 larger except for ketals, and those of ethanol were roughly 2000–10,000 larger compared with that of high-molecular weight compound (PVA). It can be well explained that these differences in the rate constant depend on their entropy and the mobility of molecules. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1719–1931, 1997     

Metastable liquid–liquid and solid–liquid phase boundaries in polymer–solvent–nonsolvent systems

In general liquid–liquid demixing processes are responsible for the porous morphology of membranes obtained by immersion precipitation. For rapidly crystallizing polymers, solid–liquid demixing processes also generate porous morphologies. In this study, the interference of both phase transitions has been analyzed theoretically using the Flory–Huggins theory for ternary polymer solutions. It is demonstrated that four main thermodynamic and kinetic parameters are important for the structure formation in solution: the thermodynamic driving force for crystallization, the ratio of the molar volumes of the solvent and the nonsolvent, the polymer–solvent interaction parameter, and the rate of crystallization of the polymer compared to the rate of solvent-nonsolvent exchange. An analysis of the relevance of each of these parameters for the membrane morphology is presented. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 763–770, 1997     

Model reactions and formation of epoxy networks with the phenylbenzoate mesogen

The phenylbenzoate mesogen was introduced into epoxy networks by the crosslinker 4-hydroxyphenyl-4-hydroxybenzoate and by the diglycidylether of 4-hydroxyphenyl-4-hydroxybenzoate, respectively. Rigid networks were synthesized on the basis of 4-hydroxyphenyl-4-hydroxybenzoate and the diglycidylether of bisphenol A, and flexible networks were prepared by reaction of the diglycidylether of butanediol-1.4 with the same dihydroxy compound. Model investigations were used to obtain information about the reactivity differences of the phenolic hydroxyl groups of the bisphenol used for network formation. Furthermore, the thermal properties of the main products isolated from the model reactions are strongly influenced by the substituents at the phenylbenzoate structure. Some of these model substances demonstrate structures that can be also found in the networks. In addition, photoinduced cationic crosslinking of the diglycidylether of 4-hydroxyphenyl-4-hydroxybenzoate results in networks with different thermal properties that are dependent on the temperature of network formation. Moreover, the temperature used during crosslinking influences the formation of ordered structures in the networks. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2653–2688, 1997     

Photophysics of carbazole-containing systems. 1. Dilute solution behavior of poly(N-vinyl carbazole) and N-vinyl carbazole/methyl acrylate copolymers

Steady-state and time-resolved fluorescence techniques have been used to study the photophysical behaviors of poly(N-vinyl carbazole), PNVCz and a series of N-vinyl carbazole-methyl acrylate (NVCz-co-MA) copolymers in dilute solution as a function of both NVCz composition and temperature. A kinetic scheme, intended to describe intramolecular excimer formation across the entire NVCz composition range, is proposed. In low aromatic content copolymers, two monomer species (unquenched and quenched monomer) and two excimer species (the sandwich-like excimer and a higher energy excimer) exist. The contribution from monomer emission to the overall fluorescence decreases with increasing NVCz content through increased excimer formation: this is likely to be consequent upon (1) an increase in the number of excimer forming sites, and (2) increasing efficiency of energy transfer from the excited monomers to the excimer forming sites. In the homopolymer, PNVCz, the only emission that can be observed on a nanosecond timescale is excimeric. This fluorescence appears to originate from three excimer species (the sandwich-like excimer, and two higher energy forms). For the homopolymer, the current observations are consistent with the model proposed by Vandendriessche and De Schryver [Polym. Photochem. 7 , 153 (1986)]. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 963–978, 1997     

Rubber particle agglomeration phenomena in acrylonitrile-butadiene-styrene (ABS) polymers II. Rubber particle agglomeration elucidated by a thermodynamic theory

A thermodynamic theory incorporating Flory-Huggins thermodynamics was developed to elucidate the observed rubber particle agglomeration phenomena in ABS molded under a severe condition. When the particle size of ABS is smaller than a thermodynamically stable domain size (D_s), rubber particle agglomeration can occur. Based on this criterion, rubber particle agglomeration can be explained semiquantitatively, especially for materials which do not have too insufficient graft level and nearly no compositional acrylonitrile mismatch. This finding suggests that the agglomeration results mainly from a driving force produced by thermodynamic incompatibility between components. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 553–562, 1997     

Synthesis and functionalities of poly(N-vinylalkylamide). IV. Synthesis and free radical polymerization of N-vinylisobutyramide and thermosensitive properties of the polymer

Pyrolysis of (N-α-isopropoxyethyl)isobutyramide, which was obtained by the reaction of isobutyramide, 2-propanol, and acetaldehyde in the presence of conc. sulfuric acid, produced N-vinylisobutyramide (NVIBA). The free radical polymerization of NVIBA was carried out in various solvents in the presence of a radical initiator. It was found that the polymerizability of NVIBA is similar to that of N-vinylacetamide. The resulting polyNVIBA showed a lower critical solution temperature (LCST) sharply at 39°C. Thermosensitive properties of polyNVIBA were investigated in comparison with poly(N-isopropylacrylamide). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1763–1768, 1997     

Photocrosslinkable vinylamine copolymers. I. Synthesis and photosensitivity of cinnamoylated polyvinylamine

Vinylamine copolymers prepared by the Hofmann reaction were functionalized by amidification with cinnamoyl chloride. The resulting photosensitive polymers, which are the nitrogen analogues of poly(vinylcinnamate), can be prepared with various contents of cinnamamide side groups. The polymers exhibit a marked hydrophilicity and undergo efficient crosslinking upon exposure to 250–300 nm UV light. The sensitivity S expressed in cm²·J⁻¹ was shown to be higher for a given content, τ, in cinnamamide groups expressed in mol·g⁻¹ when the residual vinyl amine units are in the ammonium form. The dependence of S upon τ was of the second order for the free base form of the photopolymers, but a higher order with S approximately proportional to τ³ for the hydrochloride form of the photosensitive polymers. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2513–2520, 1997