Hanqiao Feng

A high resolution solid-state n.m.r. and d.s.c. study of miscibility and crystallization behaviour of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) blends

Abstract Blends of crystallizable poly(vinyl alcohol) (PVA) with poly( N -vinyl-2-pyrrolidone) (PVPy) were studied by 13 C cross-polarization/magic angle spinning (CP/MAS) n.m.r. and d.s.c. The 13 C CP/MAS spectra show that the blends were miscible on a molecular level over the whole composition range studied, and that the intramolecular hydrogen bonds of PVA were broken and intermolecular hydrogen bonds between PVA and PVPy formed when the two polymers were mixed. The results of a spin-lattice relaxation study indicate that blending of the two polymers reduced the average intermolecular distance and molecular motion of each component, even in the miscible amorphous phase, and that addition of PVPy into PVA has a definite effect on the crystallinity of PVA in the blends over the whole composition range, yet there is still detectable crystallinity even when the PVPy content is as high as 80 wt%. These results are consistent with those obtained from d.s.c. studies.

Compatibilization effect of graft copolymer on immiscible polymer blends: 1. LLDPE/SBS/LLDPE-g-PS systems

Abstract The compatibilizing effect of graft copolymer, linear low density polyethylene-g-polystyrene (LLDPE- g -PS), on immiscible blends of LLDPE with styrene-butadiene-styrene triblock copolymer (SBS) has been investigated by means of 13 C CPMAS n.m.r. and d.s.c. techniques. The results indicate that LLDPE- g -PS is an effective compatibilizer for LLDPE/SBS blends. It was found that LLDPE- g -PS chains connect two immiscible components, LLDPE and SBS, through solubilization of chemically identical segments of LLDPE- g -PS into the amorphous region of LLDPE and PS block domain of SBS, respectively. It was also found that LLDPE- g -PS chains connect the crystalline region of LLDPE by isomorphism, with serious effects on the supermolecular structure of LLDPE. The effect of LLDPE- g -PS on the supermolecular structure of LLDPE in the LLDPE/SBS blends obviously depends on the composition of the blends, but has little dependence on the PS grafting yields of LLDPE- g -PS.

The aggregation state of polyimide

The aggregation slate of polyimide in solution and in the solid state were studied using the NMR and fluorescence techniques. The experiment results show that the decay of spin-spin relaxation of polyimides with concentration can be described as a single exponential, biexponential, triexponential, biexponential profile. Meanwhile, the intensities of fluorencence spectra increase rapidly with the concentration, and some peaks have a red-shift. Based upon these experiment results, it can be concluded that polyimide in solution is very flexible, and there are several critical concentrations at which polyimide has distinctly different aggregation states. The existence of intermolecular charge transfer interaction between polyimide chains has been proved, and the interaction has a profound effect on the glass transition temperature, T-g, and the dynamic mechanical modulus of polyimide

Miscibility and specific interactions in poly(β-hydroxybutyrate-co-β-hydroxyvalerate) and poly(p-vinylphenol) blends

The blends of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (P(HB-co-HV)/poly(p-vinylphenol)(PVPh) were investigated by differential scanning calorimetry (DSC), Fourier transform IR (FT-IR) spectroscopy and high-resolution solid-state C-13 NMR techniques. Single glass transition temperatures existing in the whole composition range indicates that these blends are miscible. The presence of hydrogen bonding between the hydroxyl of PVPh and carbonyl of P(HB-co-HV), shown by FT-IR spectra, is the origin of the miscibility. Furthermore, results obtained by high-resolution solid-state C-13 NMR give more information about the structure of the blends

The miscibility of homopolymer/random copolymer blends—3. Blends of SAA with polymethacrylates and polyesters

The miscibility of blends of poly(styrene-co-allyl alcohol) (SAA) with poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(n-butyl methacrylate) (PnBMA), poly-epsilon-caprolactone (PCL) or polycarbonate (PC) has been studied by means of NMR, FT-IR and DSC techniques. It was found that SAA and PMMA, PEMA or PCL form miscible blends and SAA is only partially miscible with PC or PnBMA. Both phenyl groups and hydroxyl groups in SAA are involved in the intermolecular interactions between SAA and PMMA, PEMA or PCL. Also the hydroxyl-carbonyl hydrogen bonds existing in all the miscible blends studied are formed partially at the expense of the disruption of self-association of hydroxyl groups in pure SAA