Viscosity behaviour of poly(ethyl methacrylate) in the ethyl acetate/tert-butanol binary mixture: total and preferential adsorption

The behaviour of poly(ethyl methacrylate) (PEMA) in the ethyl acetate (1)/tert-butanol (2) binary mixture is studied by laser light scattering, differential refractometry and viscometry. Ethyl acetate is a solvent for the polymer and tert-butanol is a precipitant. Preferential adsorption of tert-butanol up to 15% alcohol in the binary mixture is observed, ethyl acetate being preferentially adsorbed in the macromolecular coil at higher percentage of alcohol in the solvent mixture. Total adsorption of PEMA is independent of the amount of tert-butanol in the solvent. Various theoretical expressions for the preferential and total adsorption coefficients are used; their agreement or disagreement with the experimental results is explained on the basis of polymer-solvent interactions.     

Viscometric behaviour of hydrophobically modified poly(sodium acrylate)

Summary Hydrophobically associating poly(acrylic acid) was obtained by reaction of a small amount of octadecylamine on the carboxyl groups of the polymer. In pure water, this modified polymer exhibits a very high thickening power. By increasing the ionic strength of the aqueous solution a strong viscosity increase can be obtained instead of the decrease classically observed with polyelectrolytes. For instance, in 1% NaCl the modified poly(sodium acrylate) is of several orders of magnitude more viscous than the precursor polymer.     

Mark-Houwink-Sakurada coefficients for conventional poly(methyl methacrylate) in tetrahydrofuran

Summary Intrinsic viscosities [] in tetrahydrofuran (THF) at 30°C are reported for ten narrow molecular weight distribution poly(methyl methacrylate) (PMMA) samples covering nearly two orders of magnitude in molecular weight. By combining the viscosity results with absolute weight-average molecular weights determined via low-angle laser light scattering (LALLS) experiments, we have accurately determined the Mark-Houwink-Sakurada (MHS) parameters for this polymer-solvent pair (K=7.56x10⁵ and a=0.731, when [] is in dL g^-1).     

Comparison of the phase behaviour of the liquid-crystalline polymer/poly(methyl methacrylate) and poly(vinyl acetate)/poly(methyl methacrylate) blends

The phase behaviour of blends of a liquid-crystalline polymer (LCP) and poly(methyl methacrylate) (PMMA), as well as the phase state of blends of PMMA and poly(vinyl acetate) (PVA) has been investigated using light scattering and phase-contrast optical microscopy. The blends of LCP and PMMA have been obtained by coagulation from ternary solutions. The cloud point curves were determined. It was established that both pairs demix upon heating, ie have an LCST. In the region of intermediate composition, the phase separation proceeds according to a spinodal mechanism; however for LCP/PMMA blends, the decomposition proceeds according to a non-linear regime from the very onset. In the region of small amounts of LCP, the phase separation follows a mechanism of nucleation and growth. For PMMA/PVA blends, the spinodal decomposition proceeds according to a linear regime, in spite of the molecular mobility that PVA chains develop at lower temperatures. Only after prolonged heat treatment does the process transit to a non-linear regime. The data show a similarity between the phase behaviour of blends of liquid-crystalline and of flexible amorphous polymers. The distinction consists of the absence of a linear regime of decomposition for LCP-PMMA blends. © 1999 Society of Chemical Industry     

Phase behaviour in poly(ethylene oxide-b-t-butyl methacrylate) block copolymers

The lamellar thickness of the poly(ethylene oxide)-poly(t-butyl methacrylate) (PEO-PTBMA) diblock copolymer system, obtained by differential scanning calorimetry and small angle X-ray scattering investigations, is correlated with the degree of polymerization of the amorphous (PTBMA) and crystallizable (PEO) sequences. The non-equilibrium exponents obtained immediately after bulk crystallization are different to those from extrapolated equilibrium results. Within the experimental standard deviations, the theoretical predictions of DiMarzio et al. and of Whitmore and Noolandi could be confirmed. The molecular weights of PEO and PTBMA ranged from 250 to 21000 g mol⁻¹ and from 1500 to 17000 g mol⁻¹, respectively. Both the equilibrium lamellar thickness l and the PEO domain size d_PEO increase with increasing PEO and decreasing PTBMA degrees of polymerization Z according to d_PEO l Z^0.97±0.08_EOZ^{−(0.53±0.19)}_TBMA.     

LCST behaviour in blends of poly(vinylidene fluoride) and isotactic poly(ethyl methacrylate)

Blends of poly(vinylidene fluoride) (PVF₂) with isotactic, atactic or syndiotactic poly(ethyl methacrylate) (it-, at- or st-PEMA) were studied by calorimetry and light microscopy. The occurrence of single glass transitions over a broad composition, as well as the lowering of the crystallization temperature upon cooling from the melt, indicate a complete compatibility in the amorphous state in blends of PVF₂ with at- and st-PEMA up to high temperatures. With it-PEMA, however, phase separation took place when the temperature was raised, sugesting LCST behaviour. Cloud points appeared in the temperature range of 150–200°C, making this system suitable for phase separation studies. The occurrence of double glass transitions as well as double crystallization exotherms in some $\text{PVF}{}_2\text{it-PEMA}$ blends could be explained from the phase diagram and the slowness of phase mixing upon cooling.     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(methyl methacrylate)

Summary Poly(n-propyl methacrylate) is known to be immiscible with poly(methyl methacrylate) (PMMA). However, we have found that poly(methoxymethyl methacrylate) is miscible with PMMA, indicating the importance of ether oxygen atoms in achieving miscibility. On the other hand, poly(methylthiomethyl methacrylate) is immiscible with PMMA.     

Dielectric relaxation behaviour of poly(cyclobutyl methacrylate)s

Dielectric behaviour of two poly(methacrylate)s with cyclobutyl groups in the side‐chains has been studied. This investigation was performed by determining the dielectric permittivity and loss in terms of frequency and temperature for poly(cyclobutyl methacrylate) (PCBuM) and poly(cyclobutylmethyl methacrylate) (PCBuMM). Dynamic dielectric measurements show sub‐glass relaxations, probably due to motions in the lateral chain, including the cyclobutyl ring. The effect of the insertion of a flexible spacer group into the side‐chain is also analyzed. The α relaxations were analyzed in terms of the Havriliak–Negami equation and the free volume theory tested according to the Vogel–Fulcher–Tamman–Hesse equation. The conductive and interfacial phenomena were studied by hopping and MacDonald–Coelho models. © 2002 Society of Chemical Industry     

Anisotropic hygroelastic behaviour of oriented poly(methyl methacrylate)

A series of samples of oriented poly(methyl methacrylate) was prepared by drawing at a range of temperatures above T_g to a constant extension ratio. The birefringence was used as a measure of orientation. The specimens were immersed in water at 21°C and the coefficients of hygroelasticity were calculated from the dimensional change and weight gain data. Two coefficients, namely the longitudinal and the transverse, were measured for each sample. The longitudinal coefficients of hygroelasticity exhibit a linear decrease and the transverse exhibit an increase as the birefringence increases from zero. The results are analogous to those obtained for thermoelasticity (Wilson, J. D. and Treloar, L. R. G. J. Phys. (D) 1972, 5, 1614).     

Blends of poly(ethylene oxide) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate): thermal analysis, morphological behaviour and specific interactions

DSC and optical microscopy were used to determine the miscibility and crystallinity of blends of poly(ethylene oxide) (PEO) with poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM). A single glass transition temperature was observed for all blends, indicating miscibility. A progressive decrease in the degree of crystallinity and in the size of the PEO spherullites is observed, as PVPh-HEM is added. FTIR was used to probe the intermolecular specific interactions of the blends and the miscibility of the blend is mainly attributed to PVPh-HEM/PEO intermolecular interactions via hydrogen bonding.     

Stress cracking behaviour of poly(methyl methacrylate) and a poly(methyl methacrylate-ethyl acrylate) copolymer

Many organic fluids behave as stress cracking agents on polymers above a critical stress level, while remaining completely inert to the polymer below the critical stress. Because of this property, the proper selection of a stress cracking fluid and testing temperature can provide a non-destructive quality control test. Since many injection moulded parts will perform unacceptably when moulded with residual stresses above a certain level, this type of test is desirable. In this study, the effect of several organic fluids on the stress cracking behaviour of poly(methyl methacrylate) was studied. The experiments were conducted at two temperatures in order to generate a range of critical stress determining conditions. A homopolymer and copolymer of PMMA, having different molecular weight, were investigated and found to have significantly different responses to the stress cracking fluids.     

Synthesis of poly(chloroprene-co-isobutyl methacrylate) and its compatibilizing effect in polychloroprene/poly(isobutyl methacrylate) blends

A copolymer of chloroprene (CP) and isobutyl methacrylate (iBMA) [poly(CP-co-iBMA)] was prepared in benzene by radical copolymerization. For comparison, the graft copolymer of iBMA onto polychloroprene (CR) [poly(CR-g-iBMA)] was also prepared. The glass transition temperature of the poly(CP-co-iBMA) was about ?32.4°C. The monomer reactivity ratios determined by the Finneman-Ross method were given as r₁ (CP) = 1.80 and r₂ (iBMA) = 0.74 in the copolymerization of CP and iBMA, respectively. Miscibility of blends of CR and poly(isobutyl methacrylate) (PiBMA), prepared by casting from tetrahydrofuran (THF) solution, was investigated by their glass transition temperature behaviors and morphologies. Although the blends of CR and PiBMA were incompatible, the addition of poly(CP-co-iBMA) or poly(CR-g-iBMA) enhanced miscibility between the two base polymers. It was found that the extent of partial miscibility becomes larger when adding poly(CP-co-iBMA) than poly(CR-g-iBMA) as a third component to the CR/PiBMA blend of 50/50 wt % composition. © 1993 John Wiley & Sons, Inc.     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(styrene-co-acrylonitrile) and poly(p-methylstyrene-co-acrylonitrile)

The miscibility of poly(methoxymethyl methacrylate) (PMOMA) and poly(methylthiomethyl methacrylate) (PMTMA) with poly(styrene-co-acrylonitrile) (SAN) and poly(p-methylstyrene-co-acrylonitrile) (pMSAN) was studied by differential scanning calorimetry. PMOMA is miscible with SAN having an acrylonitrile (AN) content around 30 wt %. However, PMOMA is immiscible with any of the pMSAN having AN contents between 9 and 36 wt % and with pMSAN having AN contents between 19 and 34 wt %. The miscibility of the blends enables the evaluation of various segmental interaction parameters.     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(vinylidene fluoride)

Summary The miscibility behaviour of poly(methoxymethyl methacrylate) (PMOMA) and poly(methylthiomethyl methacrylate) (PMTMA) with poly(vinylidene fluoride) (PVDF) was examined by differential scanning calorimetry. PMOMA/PVDF blend system was judged to be miscible on the bases of the presence of a single, composition-dependent glass transition for the blend and a pronounced melting point depression of the PVDF component. Furthermore, lower critical solution temperature (LCST) behaviour was observed for all PMOMA/PVDF blends. PMTMA/PVDF blends were found to be immiscible. Based on the melting point depression of PVDF in PMOMA/PVDF blends, the interaction parameter B was found to be -14.5 J/cm³.     

Phase behaviour and phase separation in polymer blends of poly(methyl methacrylate) with poly(vinyl acetate)

Summary Phase behaviour and phase separation in a binary polymer blends of poly(methyl methacryate) (PMMA) with poly(vinyl acetate) (PVAc) was invistigated by cloud method and light scattering. A lower critical solution temperature (LCST) type phase diagram was found. The mixture system of PMMA/PVAc is miscible. Kinetic study on demixing at the two-phase region above the LCST was carried out by light scattering.     

Temperature-dependent interaction parameters of poly(methyl methacrylate)/poly(2-vinyl pyridine) and poly(methyl methacrylate)/poly(4-vinyl pyridine) pairs

Temperature-dependent interaction parameters (α) of poly(methyl methacrylate)/poly(2-vinyl pyridine) (PMMA/P2VP) pair and PMMA/poly(4-vinyl pyridine) (PMMA/P4VP) pair were obtained from the SAXS profiles at various temperatures, and curve fitting to the random phase approximation theory. For this purpose, symmetric P2VP-block-PMMA and P4VP-block-PMMA copolymers were synthesized anionically. The molecular weights of both block copolymers were controlled to exhibit the disordered state over the entire experimental temperatures. We found that the value of α for PMMA/P4VP was larger than PMMA/P2VP, similar to polystyrene (PS)/poly(vinyl pyridine) pairs. However, the difference between in α between PMMA/P2VP and PMMA/P4VP was much smaller than that between PS/P2VP and PS/P4VP. This might be attributed to the hydrophilic PMMA block compared with hydrophobic PS block. Finally, the order-to-disorder transition temperature for symmetric P2VP-block-PMMA copolymers was determined by small angle X-ray scattering and birefringence methods.     

Viscoelastic behaviour of epoxy resins modified with poly(methyl methacrylate)

The viscoelastic behaviour of a stoichiometric diglycidyl ether of bisphenol-A, (DGEBA), 4,4′-diaminodiphenylmethanes (DDM)s epoxy matrix modified with several amounts of poly(methyl methacrylate) (PMMA) has been studied by dynamic-mechanical analysis. Mixtures pre-cured at 80°C ranged from transparency to opacity as thermoplastic content changed from 5 to 15wt%. These changes have been attributed to variations in the ratio between polymerization rate and phase separation rate when PMMA content increased in the mixtures. When PMMA segregated from the epoxy matrix during curing, it had no influence on the crosslinking density of the epoxy phase. The clear decrease of temperature and activation energy of the β relaxation with respect to those values for the neat matrix, observed for the 5wt% PMMA-containing mixture but not for the 15wt% PMMA-containing one, are proposed to be a consequence of physical interactions between the PMMA chains and some epoxy oligomers. The dissimilar variation of the height of the ω relaxation with frequency when compared to that for the other relaxations studied, outlines the significance of physical factors influencing this relaxation. © 1998 Society of Chemical Industry     

The limits of linear viscoelasticity in poly(methyl methacrylate) and poly(ethyl methacrylate)

The limit of linear viscoelasticity is determined for poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) in uniaxial tension creep over the temperature range of 20° to T_g ?10°C. The time span covered is from 10 to 1000 sec. The linear limit is defined as the point at which the creep compliance deviates by more than 1% from its mean value in the linear viscoelastic range. For both materials, the stress limit of linear viscoelasticity falls to a minimum or plateau level at a temperature below T_g. It is suggested that the β-mechanism plays an important role in the existence of this minimum.     

Surface morphology evolution of poly(styrene-block-4-vinylpyridine) (PS-b-P4VP)(H) and poly(methyl methacrylate)-dibenzo-18-crown-6-poly(methyl methacrylate) (PMCMA) supramolecular film

Well-ordered nanostructured polymeric supramolecular thin films were fabricated from the supramolecular assembly of poly(styrene-block-4-vinylpyridine) (PS-b-P4VP)(H⁺) and poly(methyl methacrylate)-dibenzo-18-crown-6-poly(methyl methacrylate) (PMCMA). A depression of cylindrical nanodomains was formed by the block of P4VP(H⁺) and PMCMA associates surrounded by PS. The repulsive force aroused from the incompatibility between the block of P4VP(H⁺) and PMCMA was varied through changing the molecule weight (M_w) of PMCMA, the volume fraction of the block of P4VP(H⁺), and annealing the film at high temperature. Increasing the repulsive force led to a change of overall morphology from ordered nanoporous to featureless structures. The effects of solvent nature and evaporation rate on the film morphology were also investigated. Further evolution of surface morphologies from nanoporous to featureless to nanoporous structures was observed upon exposure to carbon bisulfide vapors for different treatment periods. The wettability of the film surface was changed from hydrophilicity to hydrophobicity due to the changes of the film surface microscopic composition.