Microdomain control in graft copolymer and polymer blends by means of epitaxial growth

Poly(vinyl acetate) (PVAc) and poly(tert-butyl methacrylate) (PBMA) macromonomers with vinyl end-groups were synthesized by radical or anionic polymerizations. 4-Vinylpyridine (4VP)/vinyl acetate (VAc) and 4VP/tert-butyl methacrylate (BMA) graft copolymers were prepared by radical copolymerization of these macromonomers with 4VP as a comonomer. The 4VP/vinyl alcohol (VA) graft copolymer was derived from alkaline hydrolysis of 4VP/VAc graft copolymer. After having fixed the microdomains of 4VP/VA graft copolymer film, the solution of graft copolymer (or polymer blends) was cast on a support film of 4VP/VA graft copolymer. It was shown that the domain structure of the upper layer is governed by epitaxial growth of the microdomain pattern of the support film surface.     

Miscibility of poly(vinyl chloride) with ethylene/N,N-dimethylacrylamide copolymers.

The incorporation of N,N-dimethylacrylamide (DMA) as a comonomer in polyethylene yields a material possessing dramatically improved mechanical compatibility with poly(vinyl chloride) (PVC). At increased levels of DMA (25–30 wt.-%) miscibility with PVC is achieved. This behavior is believed to be due to the specific interaction of the tertiary hydrogen of poly(vinyl chloride) (weak “acid” or proton donor) with the disubstituted amide in the ethylene copolymer (weak “base” or proton acceptor). Dynamic mechanical characterization of the ethylene/DMA copolymer (EDMA)/PVC blends reveals separate glass transitions temperatures at DMA levels below 20 wt.-%; they merge into a single T_g when the DMA content reaches a value above 25 wt.-% in the ethylene copolymer. The secondary loss transition for PVC (?40°C) is lowered in temperature and greatly suppressed in magnitude. This is further evidence of molecular miscibility. Mechanical property data obtained on the EDMA/PVC blends are consistent with the foregoing considerations.     

Formation of conjugated polyenes by chemical and thermal degradation of vinyl chloride copolymers and other vinyl polymers

Raman and infrared spectroscopic studies on the chemical degradation products of two vinyl chloride/vinyl acetate copolymers and a vinyl chloride/vinyl acetate/vinyl alcohol terpolymer, obtained with the system potassium tert-butoxide/N,N-dimethylformamide, show that substantially complete dehydrochlorination occurs. Although the vinyl acetate groups are hydrolysed to the corresponding alcohol these latter largely remain intact and block the extension of the polyene sequences, whose lengths, measured by Raman spectroscopy, are in agreement with values calculated from the initial polymer composition. No degradation other than hydrolysis occurs with vinyl acetate and vinyl alcohol homopolymers or a vinyl alcohol/vinyl acetate copolymer. The thermal degradation of the copolymers containing vinyl chloride, and of two vinyl chloride homopolymers of differing syndiotacticity, at 153°C in N,N-dimethylformamide, gives both dehydrochlorination and elimination of the comonomer units, the latter reaction occurring at least as rapidly as the former. A crosslinked structure, in which there is some steric stabilisation and, hence, conjugated polyene sequence lengths up to about 40, is formed. A maximum sequence length of 8 is found in thermally degraded poly(vinyl acetate), but the conjugated polyenes are too short to be detected in degraded poly(vinyl alcohol) and the vinyl alcohol/vinyl acetate copolymer.     

Miscibility and specific interactions in blends of poly(vinyl acetate-co-vinyl alcohol) with poly(ethyloxazoline)

Miscibility of poly(ethyloxazoline) (PEOX) with poly(vinyl acetate) (PVAC), poly(vinyl alcohol) (PVAL) and poly(vinyl acetate-co-vinyl alcohol) (ACAL copolymers) has been investigated over a wide composition range. In some blends, due to the small difference between the glass transition temperatures of the components, the enthalpic relaxation method was used as miscibility criterion. Differential scanning calorimetry (DSC) results indicate that PEOX is immiscible with PVAC and PVAL but is miscible with ACAL copolymers in a certain range of compositions. The ACAL/PEOX phase diagram for different copolymer compositions has been determined. The variation of the glass transition temperature with blend composition for miscible systems was found to follow the Kwei equation. Infrared spectroscopy studies of blends reveal the existence of specific interactions via hydrogen bonding between hydroxyl groups in vinyl alcohol units and the carbonyl group in the tertiary amide, which appear to be decisive for miscibility.     

Synthesis of poly(vinyl alcohol)/poly(dimethylsiloxane) graft copolymer

Poly(vinyl acetate)/poly(dimethylsiloxane) graft copolymer ( 4a ), with a controlled poly(dimethylsiloxane) graft chain length, was synthesized by radical copolymerization of vinyl acetate with poly(dimethylsiloxane) ( 3 ) having a dimethylvinylsilyl end group. 3 was prepared by living anionic polymerization of hexamethylcyclotrisiloxane ( 1 ) with butyllithium and subsequent termination with chlorodimethylvinylsilane ( 2 ). Poly(vinyl alcohol)/poly(dimethylsiloxane) graft copolymer ( 4b ) was then synthesized by selective saponification of the poly(vinyl acetate) segments in the graft copolymer 4a with K₂CO₃ in methanol.     

Effect of a triblock PCL-PDMS-PCL copolymer on the properties of immiscible poly(vinyl chloride)/poly(2-ethylhexyl acrylate) blends

Miscibility, thermal, mechanical and morphological properties of poly(vinyl chloride)/poly(2-ethylhexyl acrylate), (PVC/PEHA) blends containing 1–10 wt.-% of the triblock copolymer polycaprolactone-block-poly(dimethylsiloxane)-block-polycaprolactone (PCL-PDMS-PCL, Tegomer) were investigated by several techniques. Binary blends of PVC/PEHA are found to be immiscible according to differential scanning calorimetry and viscosity measurements. The effect of Tegomer addition on the properties of blends was examined. Ternary blends of PVC/PEHA/Tegomer exhibited a single T_g behaviour and viscosity measurements indicate some compatibility. Stress-strain results showed that Tegomer has a synergetic effect on the flexibility of the blends. FTIR analysis confirms the specific interactions between the components in ternary blends of PVC/PEHA/Tegomer. Morphological properties of the blends were examined by scanning electron microscopy.     

Graft copolymers from modified ethylene/vinyl acetate copolymers, 2. Synthesis of polystyrene-grafted poly[ethylene-co-(vinyl acetate)] and evaluation of its compatibilizing effect in polystyrene/poly[ethylene-co-(vinyl acetate)] blends

Polystyrene-grafted poly[ethylene-co-(vinyl acetate)] (EVA-g-PS) has been synthesized from functionalized polystyrene containing acyl chloride end group (PS-COCl) and partly (5%) hydrolyzed poly[ethylene-co-(vinyl acetate)] (EVALVA-5%). The graft efficiency is ca. 100% when low-molecular-weight polystyrene is employed. By increasing the molecular weight of the grafts the efficiency decreases. These graft copolymers have been used for compatibilizing polystyrene (PS)/poly[ethylene-co-(vinyl acetate)] (EVA) blends. The ability of the copolymers as compatibilizing agent has been verified by an analysis of the mechanical properties and by scanning electron microscopy.     

Thermal,Mechanical, Electrical and Morphological Characterization Studies of Poly(vinyl chloride) Blends with Various Polyitaconates and Block Copolymers of Polyitaconates/Poly(dimethyl siloxane)

Four blends were prepared by using the solvent casting method: (1) poly(mono‐butyl itaconate)/poly(vinyl chloride) PMBI/PVC; (2) poly(mono‐cyclo hexyl itaconate)/poly(vinyl chloride) PMCHI/PVC; (3) poly(mono‐butyl itaconate)‐poly(dimethyl siloxane)‐poly(mono‐butyl itaconate)/poly(vinyl chloride) PMBI‐PDMS‐PMBI/PVC; and (4) poly(mono‐cyclo hexyl itaconate)‐poly(dimethyl siloxane)‐poly(mono‐cyclo hexyl itaconate) PMCHI‐PDMS‐PMCHI/PVC. These blends were characterized by differential scanning calorimetry (DSC), stress‐strain tests (TENSILON), dielectric thermal analysis (DETA), impedance spectroscopy (IS) and scanning electron microscopy (SEM) analyses. The results showed that the addition of about 1% poly(mono itaconates), or about 1–3% block copolymers containing PDMS blocks have clearly a plasticizing effect on PVC. All characterization methods confirm this conclusion. The addition of higher amounts of homo‐ and block copolymers causes other variations, as a results of several overlapping and synergetic effects.     

Glass transition temperatures in blends of poly(N-vinyl-2-pyrrolidone) with a copolymer of bisphenol A and epichlorohydrin or with poly(vinyl butyral)

Blends of poly(vinyl butyral) (PVB) and of a copolymer of bisphenol A and epichlorohydrin (Phenoxy) with poly(N-vinyl-2-pyrrolidone) (PVP) were prepared by solution casting. The glass transition temperatures T_g for different compositions of the blends were measured by differential scanning calorimetry (DSC). The T_g behaviour of PVB/PVP blends suggests the existence of a single phase for blends containing less than 50 wt.-% PVP, and of two phases in blends containing more than 50 wt.-% PVP. Phenoxy/PVP blends showed to be miscible over the entire composition range. It was found that the Gordon-Taylor equation predicts adequately the T_g-composition dependence with a K parameter equal to 0,5 and 1,25 for PVB/PVP and Phenoxy/PVP blends, respectively.     

Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenylene oxide)/chlorinated polyethylene blends

The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.     

Behaviour of permeation and separation for aqueous organic acid solutions through poly(vinyl chloride) and poly[(vinyl chloride)-co-(vinyl acetate)] membranes

The permeation and separation characteristics of poly(vinyl chloride) (PVC) and poly[(vinyl chloride)-co-(vinyl acetate)] (poly(VC-co-VAc)) membranes were investigated for aqueous organic acid solutions by pervaporation and evapomeation. The PVC membrane preferentially incorporates organic acids and predominantly permeates water from aqueous organic acid solutions. Water permselectivities of these aqueous solutions through the PVC membrane are significantly dependent on high diffusivity of water across the membrane. It was found that the permeation rate increases and the separation factor for the water permselectivity decreases with increasing vinyl acetate (VAc) content in the poly(VC-co-VAc) membrane. Preferential solubility of acetic acid into the poly(VC-co-VAc) membrane increases with the VAc content. This result was explained by a strong affinity between acetic acid and the VAc unit in the poly(VC-co-VAc) membrane.     

Interpolymer complexes of a graft copolymer with polyelectrolytes and equivalent blends of binary homopolymer complexes: A comparative study of their stability and thermodynamic parameters

Interpolymer complexes of acrylamide/vinyl alcohol graft copolymers (AAm/VA) were prepared with two typical polyelectrolytes, e. g. poly(methacrylic acid) (PMA) and poly(ethyleneimine) (PEI). The equivalent blends of the same composition as the graft copolymer complexes were also prepared by mixing stoichiometric portions of binary homopolymer complexes. The stability constant (K), degree of linkage (θ) and related thermodynamic parameters (e. g. standard free energy change ΔG⁰, standard enthalpy change ΔH⁰ and standard entropy change ΔS⁰) were determined for each system by using Osada's method. The comparative study between graft copolymer complexes and equivalent blends indicated a considerable difference in these parameters. An interpretation of this discrepancy was sought in terms of copolymer effect, neighbouring group influence, and the nature of secondary binding forces upon interpolymer complexation.     

Miscibility of mixtures from partially hydrolyzed poly(vinyl acetate) and poly(N-vinyl-2-pyrrolidone)

Polymers with different compositions of vinyl alcohol and vinyl acetate units (P(VA-VAc)), obtained by alcoholysis of poly(vinyl acetate) with sodium methoxide, were mixed with poly(N-vinyl-2-pyrrolidone) (PVP). The miscibility was studied observing glass transition temperatures by differential scanning calorimetry (DSC). The calorimetric results indicate that for vinyl alcohol unit contents in P(VA-VAc) of roughly 70 wt.-% or more, P(VA-VAc)/PVP blends are fully miscible, whereas blends obtained from P(VA-VAc) with vinyl alcohol contents lower than the above mentioned values are only partially miscible or even immiscible. The miscibility is attributed to hydrogen bond interactions between hydroxyl groups in P(VA-VAc) and the carbonyl group of PVP.     

The miscibility and phase separation in binary blends of poly(vinyl chloride) with methyl methacrylate/acrylonitrile copolymers

The miscibility of poly(vinyl chloride) with poly(methyl methacrylate-stat-acrylonitrile) has been studied. Poly(vinyl chloride) is miscible with methyl methacrylate/acrylonitrile copolymers having acrylonitrile contents between 2,0 and 17 wt.-%. All calculated binary segmental interaction parameters were positive, suggesting immiscibility of the corresponding binary homopolymer blends.     

Etude du couplage chromatographie d'exclusion — diffusion de la lumière, 2. Application a quelques problèmes particuliers

A continuous light scattering detector coupled to a gel permeation chromatography (GPC) instrument (GPC-LS), as described in the preceding paper, is used to determine the hydrodynamic structure factor g′ of branched polystyrene samples and to establish the viscosity law for poly(methyl methacrylate), poly(vinyl chloride), and poly(vinyl acetate) by comparing the results from GPC-LS and GPC analysis (with molar mass calibration with linear, monodisperse polystyrene samples).     

Polymer fractionation by gel permeation chromatography

The molecular weight distributions of polystyrene, poly(vinyl chloride), polychloro-prene and polyethylene have been determined by gel permeation chromatography using silica gel as the stationary phase. The factors affecting fractionation efficiency, such as column dimensions and polymer loading are discussed. Fractionation efficiency for polystyrene, poly(vinyl chloride) and polychloroprene is comparable to that obtained from such established methods as fractional precipitation and fractional elution. For polyethylene, however, the gel permeation technique using silica gel as the stationary phase, does not appear to have the fractionation efficiency of the column elution method of FRANCIS, COOKE, and ELLIOTT.     

Comparison of intermolecular interaction and compatibility in the blends of poly(ϵ-caprolactone) with poly(vinyl chloride), poly(bisphenol A carbonate) and poly(hydroxy ether of bisphenol A)

The crystallization behavior of poly(ε-caprolactone) (PCL) in the miscible blends of PCL/poly(vinyl chloride), PCL/poly(hydroxy ether of bisphenol A) and PCL/poly(bisphenol A carbonate) has been investigated by differential scanning calorimetry and polarized light microscopy. Through comparison of the PCL crystallization rate and calculation of the interaction energy density B between the miscible components in these blends, it was found that the effect of the noncrystallizable component on the crystallizability of PCL is not consistent with the strength of the specific interaction in the blends detected by FTIR but coincides with the interaction energy density B. The variation of PCL crystallizability reflects an effect of the “apparent total intermolecular interaction” in the blends. The influences of glass transition temperature, self-associated interaction of the noncrystallizable component and geometrical factors on the PCL crystallization rate and the intermolecular interaction in the blends are also discussed.     

Synthesis of poly(vinyl alcohol)-graft-polystyrene

The reaction of living polystyrene, prepared with butyllithium as an initiator in a tetrahydrofuran/benzene (vol. ratio 1/1 or 2/1) solution at ?30°C or ?50°C, with chlorodimethylvinylsilane was carried out to prepare polystyrene with narrow molecular-weight distribution and with a vinylsilane end group ( 1 ). The radical copolymerization of vinyl acetate with 1 in ethyl acetate solution yields poly(vinyl acetate)-graft-polystyrene ( 2 ) of controlled graft segement length. The subsequent saponification of 2 with NaOH in methanol provides poly(vinyl alcohol)-graft-polystyrene ( 3 ).     

Preparation and properties of terpolymers of ethylene,vinyl acetate and vinyl alcohol

Several terpolymers of ethylene, vinyl acetate and vinyl alcohol have been prepared by controlled transformation into hydroxyls of the acetate groups of an ethylene‐vinyl acetate copolymer (with 28 wt.‐% in vinyl acetate). The degree of transformation has been determined by ¹H NMR. Samples covering the entire range of transformations have been obtained, and their properties have been analyzed by DSC and X‐ray diffraction. The results show a marked increase of both melting temperature and crystallinity as the degree of transformation increases, owing to the fact that the vinyl alcohol units are able to cocrystallize in the polyethylene lattice, while the acetate groups are excluded.     

Effect of filler on kinetics and energy of activation of phase separation in poly(methyl methacrylate)/poly(vinyl acetate) blend

The effect of a filler on the rate and energy of activation of phase separation was studied for binary poly(methyl methacrylate)/poly(vinyl acetate) blends (system with LCST) using light scattering. It was found that the rate of phase separation of the filled blends at close quench depth ΔT = T–T_s is much lower as compared with the unfilled one at close quench depth. The activation energy for the filled blends is lower than that of unfilled blends. The drop of the rate of phase separation and of the activation energy in filled systems is explained by the formation of a border layer at the interface with solid where molecular packing is less dense and molecular mobility is restricted in comparison with unfilled polymer. Equal rates of phase separation or the equilibrium state may be achieved at higher quench depth for the filled blend.