Polymer/silica nanoscale hybrids through sol-gel method involving emulsion polymers. 1. Morphology of poly(butyl methacrylate)/SiO2

In this article, we report on an approach of using an emulsion polymerized polymer in preparing organic-inorganic nanocomposites through a sol-gel technique. By mixing a polymer emulsion with prehydrolyzed tetraethoxysilane transparent poly(butyl methacrylate)/SiO2, nanocomposites were prepared as shown by TEM. AFM, FTIR, and XPS results show that there is a strong interaction between polymer latex particles and the SiO2 network. Comparison of the emulsion method with a traditional solution method shows that nanocomposites can be prepared by both methods, but there is some difference in their morphology and properties.

Spatially-confined crystallization of poly(vinylidene fluoride)

Nanometre-sized poly(vinylidene fluoride) (PVDF) particle domains in a confined space were obtained by blending PVDF with excess poly(methyl methacrylate) (PMMA). When these particles were small enough they showed beta -form structure, which was different from the structure of bigger particles or PVDF bulk. However, the beta -form was thermodynamically metastable because it could eventually be transformed to a more stable phase by annealing at a certain temperature. Larger particle domains were of identical phase to the bulk, indicating that small size favours the formation of the beta -form. (C) 2000 Society of Chemical Industry.

Miscibility, crystallization kinetics, and morphology of poly(beta-hydroxybutyrate) and poly(methyl acrylate) blends

The miscibility, spherulite growth kinetics, and morphology of binary blends of poly(beta-hydroxybutyrate) (PHB) and poly(methyl acrylate) (PMA) were studied with differential scanning calorimetry, optical microscopy, and small-angle X-ray scattering (SAXS). As the PMA content increases in the blends, the glass-transition temperature and cold-crystallization temperature increase, but the melting point decreases. The interaction parameter between PHB and PMA, obtained from an analysis of the equilibrium-melting-point depression, is -0.074. The presence of an amorphous PMA component results in a reduction in the rate of spherulite growth of PRE. The radial growth rates of spherulites were analyzed with the Lauritzen-Hoffman model. The spherulites of PHB were volume-filled, indicating the inclusion of PMA within the spherulites. The long period obtained from SAXS increases with increased PMA content, implying that the amorphous PMA is entrapped in the interlamellar region of PHB during the crystallization process of PHB. All the results presented show that PHB and PMA are miscible in the melt. (C) 2000 John Wiley & Sons, Inc.

Polymerization of methyl methacrylate with organolanthanides as single-component catalysts

It was first found that Ind(2)Y(mu -Et)(2)AlEt2 and Ind(2)LnN(i-Pr)(2) (Ln = Y, Yb) exhibit extremely high catalytic activity in the polymerization of methyl methacrylate. The reactions can be carried out over a quite broad range of polymerization temperatures from -30 to 50 degreesC. PMMA with high molecular weight (7.8 x 10(-5)) and high isotacticity (94%) can be obtained by using Ind(2)Y(mu -Et)(2)AlEt2, and narrow molecular weight distribution (M-w/M-n < 1.5) can be obtained by using Ind(2)LnN(i-Pr)(2) (Ln = Y, Yb).

Blends of linear low-density polyethylene and a diblock copolymer of hydrogenated polybutadiene and methyl methacrylate

Blends of linear low-density polyethylene (LLDPE) and a diblock copolymer of hydrogenated polybutadiene and methyl methacrylate [P(HB-b-MMA)] were studied by transimission electron microscope (TEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). At 10 wt% block copolymer content, block copolymer chains exist as spherical micelles and cylindrical micelles in LLDPE matrix. At 50 wt% block copolymer content, block copolymer chains mainly form cylindrical micelles. The core and corona of micelles consist of PMMA and PHB blocks, respectively. DSC results show that the total enthalpy of crystallization of the blends varies linearly with LLDPE weight percent, indicating no interactions in the crystalline phase. In the blends, no distortion of the unit cell is observed in WAXD tests.

The polymerization of methyl methacrylate with a new Nd(O-i-Pr)(3)-Al(i-Bu)(3) catalyst system

Methyl methacrylate (MMA) was polymerized with the rare earth coordination catalyst-system of Nd(O - i-Pr)(3) in toluene. The influences of various ligands in neodymium complexes, molar ratio of Al/Nd, catalyst concentration, catalyst aging time, solvents, the third component CCl4, temperature and time on the polymerization of MMA were studied. The results showed that the polymerization conversion reached more than 80% at a catalyst concentration of 9.2 x 10(-3) mol/L. The appropriate molar ratio of CCl4/Nd was 4. Hydrocarbon was preferred for the polymerzation to obtain a high conversion and a high <(M)over bar w> of PMMA. The H-1 NMR spectra of PMMA indicated that the lower the temperature, the higher the syndiotactic content of PMMA was obtained.

Crystallization kinetics in mixtures of poly(epsilon-caprolactone) and poly(styrene-co-acrylonitrile)

Isothermal crystallization kinetics in the miscible mixtures of poly(epsilon-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) have been investigated as a function of the composition and the crystallization temperature by optical microscopy. The radial growth rates of the spherulites have been described by a kinetic equation including the interaction parameter and the free energy for the formation of secondary crystal nuclei. Fold surface free energies decrease slightly with the increase of SAN content. The experimental findings show that the influence of the glass transition temperature of the mixture, which is related to the chain mobility, on the rate of crystallization predominates over the influence of the surface free energies. This indicates that the glass transition temperature of the mixture should be of more importance, so that the growth rates decrease when the content of the noncrystallizable component increases. In addition, the Flory-Huggins interaction parameter obtained by fitting the kinetic equation with experimental data is questionable.

SYNTHESIS AND MOLECULAR-STRUCTURE OF (CH3CP)2YB.DME AND ITS CATALYTIC ACTIVITY FOR THE POLYMERIZATION OF METHYL-METHACRYLATE

The complex of (CH3Cp)2Yb . DME (DME = dimethoxyethane) has been synthesized by the reduction with metallic sodium of the corresponding chloride (CH3CP)2YbCl. (CH3CP)2Yb . DME crystallized from DME in the monoclinic space group Cm, with cell constants a = 11.068(3), b = 12.338(4), c = 12.479(4) angstrom; beta = 100.51(2)-degrees, V = 1675(l) angstrom3, and D0 = 1.66 g/cm3 for Z = 4. Least-squares refinement of 1420 unique observed reflections led to final R of 0.0487. This complex can be used as a catalyst for the polymerization of methyl methacrylate (MMA).

MISCIBILITY AND PHASE-BEHAVIOR IN BLENDS OF POLY(HYDROXYETHER OF BISPHENOL-A) WITH POLY(ETHYLENE OXIDE-CO-PROPYLENE OXIDE)

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide-co-propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60-degrees-C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean-field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting-point depression of the crystallizable component in the blends, the binary interaction energy densities, B(ij), have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen-bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility.

STUDY ON OPTICAL-ROTATORY OF HELIX POLYMER POLY(TRIPHENYLMETHYL METHACRYLATE)

The optical rotatory of helix polymer poly(triphenylmethyl methacrylate) (PTrMA) has been studied. The specific rotation of PTrMA is related with the length of helical chain linearly, while P(n)BAR<6 and P(n)BAR greater-than-or-equal-to 15. When P(n)BAR greater-than-or-equal-to 15, [alpha]D/20 = 1.6 P(n)BAR + 290-degrees. The contribution of each repeating unit to [alpha]D/20 is 1.6-degrees. In the 300-600 nm region, the ORD of PTrMA obeys both the Drude equation and Moffitt equation. The relationship between the [alpha]D of PTrMA and the solvent, concentration and temperature has also been investigated.

MUTUAL ENTANGLEMENTS IN POLY(VINYL ACETATE) POLY(METHYL ACRYLATE) INTERPENETRATING POLYMER NETWORKS

An equation has been derived for the equilibrium swelling of sequential interpenetrating polymer networks (IPNs), which exhibit a single glass transition temperature and the two components are considered to be compatible. The properties of the equilibrium swelling and elastic modulus of sequential poly(vinyl acetate)/poly(methyl acrylate) IPNs have been discussed according to the derived equation and the Siegfried-Thomas-Sperling formula of the elastic modulus for homo IPNs. In both fully swollen and bulk states, there was favourable evidence for added physical crosslinks in poly(vinyl acetate)/poly(methyl acrylate) IPNs. The Binder-Frisch theory is also discussed.

CRYSTALLIZATION OF POLY(ARYL-ETHER-ETHER-KETONE)S BLENDS

The crystallization and melting behaviour of poly(aryl-ether-ether-ketone) (PEEK) in blends with another polymer of the same family containing a bulky pendant phenolphthalein group (PEK-C) have been investigated by thermal methods. The small interaction energy density of the polymer pair (B = -8.99 J/cm3), evaluated from equilibrium melting point depression, is consistent with the T(g) data that indicate partial miscibility in the melt. Two conjugated phases are in equilibrium at 430-degrees-C: one is crystallizable and contains about 35 wt% of PEK-C; the other, containing only 15 wt% of PEEK, does not form crystals upon cooling and it interferes with the development of spherulites in the sample. The analysis of kinetic data according to nucleation theories shows that crystallization of PEEK in the explored temperature range takes place in Regime III and that a transition to Regime II might be a consequence of an increase in the amount of non-crystallizable molecules in the PEEK-rich phase. A composition independent value of the end surface free energy of PEEK lamellae has been derived from kinetic data (sigma-e = 40 +/- 4 erg/cm2) in excellent agreement with previous thermodynamic estimates. A new value for the equilibrium melting temperature of PEEK (T(m)-degrees = 639 K) has been obtained; it is about 30-degrees-C lower than the commonly accepted value and it explains better the "memory effect" in the crystallization from the melt of this high performance polymer.

Influence of plasticizer type and storage conditions on properties of poly(methyl vinyl ether-co-maleic anhydride) bioadhesive films

Poly(methyl vinyl ether-co-maleic anhydride) formed films from aqueous formulations with characteristics that are ideal as a basis for producing a drug-containing bioadhesive delivery system when plasticized with a monohydroxyl functionalized plasticizer. Hence, films containing a novel plasticizer, tripropylene glycol methyl ether (TPME), maintained their adhesive strength and tensile properties when packaged in aluminized foil for extended periods of time. Films plasticized with commonly used polyhydric alcohols, such as the glycerol in this study, underwent an esterification reaction that led to polymer crosslinking, as shown in NMR studies. These revealed the presence of peaks in the ester/carbonyl region, suggesting that glyceride residue formation had been initiated. Given the polyfunctional nature of glycerol, progressive esterification would result in a polyester network and an accompanying profound alteration in the physical characteristics. Indeed, films became brittle over time with a loss of both the aqueous solubility and bioadhesion to porcine skin. In addition, a swelling index was measurable after 7 days, a property not seen with those films containing TPME. This change in bioadhesive strength and pliability was independent of the packaging conditions, rendering the films that contain glycerol as unsuitable as a basis for topical bioadhesive delivery of drug substances. Consequently, films containing TPME have potential as an alternative formulation strategy.