A DSC study of poly(styrene-co-acrylonitrile) and poly(vinyl chloride-co-vinyl acetate) blends produced using different blending techniques

Abstract: The in situ grafting-from approach via atom transfer radical polymerization was successfully applied to polystyrene, poly(styrene-co-acrylonitrile), and polyacrylonitrile grafted onto the convex surfaces of multiwalled carbon nanotubes (MWCNTs) with (2-hydroxyethyl 2-bromoisobutyrate) as an initiator. Thermogravimetric analysis showed that effective functionalization was achieved with the grafting approach. The grafted polymers on the MWCNT surface were characterized and confirmed with Fourier transform infrared spectroscopy and nuclear magnetic resonance. Raman and near-infrared spectroscopy revealed that the grafting of polystyrene, poly(styrene-co-acrylonitrile), and polyacrylonitrile slightly affected the sidewall structures. Field emission scanning electron microscopy showed that the carbon nanotube surface became rough because of the grafting of the polymers. Differential scanning calorimetry results indicated that the polymers grafted onto MWCNTs showed higher glass-transition temperatures. The polymer-grafted MWCNTs exhibited relatively good dispersibility in an organic solvent such as tetrahydrofuran.

Abstract: Due to the hydrophobicity of poly(vinyl chloride) (PVC), the application of PVC membranes has been limited. In this paper, poly(vinyl butyral) (PVB) was introduced as the second polymer component to hydrophilized PVC ultrafiltration membranes. The miscibility of PVC/PVB blends in N,N-dimethyl acetamide were characterized by the solubility parameter, glass transition temperature of the blended membrane, casting solution viscosity, etc. The results showed that the PVC/PVB blended system was partially miscible at a certain proportion range. Water flux and hydrophilicity of the blended membranes were much better than that of the membranes made from pure PVC or PVB. A cross section of pure PVB and PVC/PVB blended membranes present an asymmetric finger-like structure, and the wall of the finger-like pore had a sponge-like structure. The addition of PVB could improve the hydrophilic property of PVC membranes, and the addition of PVC could increase the pore diameter at the bottom of PVB membranes.

Abstract: The miscibility or complexation of poly(styrene-co-acrylic acid) containing 27 mol % of acrylic acid (SAA-27) and poly(styrene-co-N,N-dimethylacrylamide) containing 17 or 32 mol % of N,N-dimethylacrylamide (SAD-17, SAD-32) or poly(N,N-dimethylacrylamide) (PDMA) were investigated by different techniques. The differential scanning calorimetry (DSC) analysis showed that a single glass-transition temperature was observed for all the mixtures prepared from tetrahydrofuran (THF) or butan-2-one. This is an evidence of their miscibility or complexation over the entire composition range. As the content of the basic constituent increases as within SAA-27/SAD-32 and SAA-27/PDMA, higher number of specific interpolymer interactins occurred and led to the formation of interpolymer complexes in butan-2-one. The qualitative Fourier transform infrared (FTIR) spectroscopy study carried out for SAA-27/SAD-17 blends revealed that hydrogen bonding occurred between the hydroxyl groups of SAA-27 and the carbonyl amide of SAD-17. Quantitative analysis carried out in the 160–210°C temperature range for the SAA-27 copolymer and its blends of different ratios using the Painter–Coleman association model led to the estimation of the equilibrium constants K2, KA and the enthalpies of hydrogen bond formation. These blends are miscible even at 180°C as confirmed from the negative values of the total free energy of mixing ΔGM over the entire blend composition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1011–1024, 2007

Abstract: The miscibility and the thermal behaviour of binary mixtures of poly(styrene- co -methacrylic acid) containing 12 or 29 mol.% of methacrylic acid (SMA-12 or SMA-29) with poly(isobutyl methacrylate- co -4-vinylpyridine) containing 20 mol.% of 4-vinylpyridine (IBM4VP-20) as blends or interpolymer complexes were investigated by differential scanning calorimetry, thermogravimetry and FTIR spectroscopy. The results showed that, depending on the nature of the solvent used in the mixture and the density of the specific interacting species introduced within the polymer matrices, miscible polymer blends or interpolymer complexes were obtained. The single T g observed with all the studied blends or interpolymer complexes is an evidence of their miscibility. The positive deviation of the T g of the blends and the complexes from the weight average of the constituents T g s and the improved thermal stability of the SMA29/IBM4VP-20 complexes as compared to their corresponding blends is mainly due to the presence of stronger specific interactions of hydrogen bonding type that occurred between the carboxylic groups of the SMA-29 and the 4-vinylpyridine of the IBM4VP-20 and to the way these specific interactions are distributed. A quantitative analysis of these interactions was carried by FTIR above the glass transition temperature of the constituents of the (85/15) SMA-29/IBM4VP-20 blend in the 1850–1570 cm −1 region.

Abstract: Cellular Materials Cellulose Cellulose, Biosynthesis Cellulose, Graft Copolymers Cellulose, Microcrystalline Cellulose Derivatives Cellulose Esters, Inorganic Cellulose Esters, Organic Cellulose Ethers Cement Additives Chain-Reaction Polymerization Chain Transfer Characterization of Polymers Charge-Transfer Complexes Chelate- Forming Polymers Chemical Analysis Chemically Resistant Polymers Chitin Chloroprene Polymers Chlorotrifluorethylene Polymers Chromatography Classification of Polymerization Reactions Coating Methods Coatings Coatings, Electrodeposition Cold Forming.

Abstract: A qualitative review of the thermodynamics of polymer systems will be given in terms of three contributions: positional (or combinatorial) entropy, an “international” term and a free volume term. From this one finds that a simple polymer-solvent system phase separates on lowering T to an Upper Critical Solution Temperature (UCST) or raising it to Lower Critical Solution Temperature (LCST), To achieve miscibility of two polymers of high molecular weight, one requires a “specific” interaction, usually a weak charge-transfer complex or a hydrogen bond. Phase separation takes place on raising the temperature to an LCST. These various UCST and LCST are predicted semi-quantitative by the Prigogine-Flory theory. When a solvent is added to two miscible polymers, a new type of phase separation appears since there is an effect of any difference in the strengths of the two polymer-solvent interactions. Phase separation may easily occur in the ternary system where there is none in the three binary systems, and examples will be given. In the case of two highly-attractive polymers in a solvent, a quite different phase separation occurs, sometimes called complex coacervation. A simple Flory-Huggins type theory predicts these phenomena in ternary systems.