Phase Structure Of Poly Research Articles

Crystal Form and Phase Structure of Poly(vinylidene fluoride)/Polyamide 11/Clay Nanocomposites by High-Shear Processing

Polyamide 11 (PA11)/clay, Poly(vinylidene fluoride) (PVDF)/clay and PVDF/PA11/clay nanocomposites were prepared by melt processing using a high shear extruder. Two types of organoclay with different modified alkyl tails and different polarities were used for PA11 and PVDF nanocomposites. PA11 nanocomposites derived from an organoclay having one alkyl tail show a well-exfoliated morphology but no crystal form transformation, whereas those derived from an organoclay having two alkyl tails give a little worse clay dispersion with the clear alpha to gamma crystal form transition with the addition of the clay. In contrast, the PVDF composites derived from the two organoclays result in a poor dispersion. In addition, PVDF/PA11 blend nanocomposites with a novel morphology have been fabricated using the high-shear extruder. It was found that the clay platelets were selectively dispersed in the PA11 phase with the size of larger than 200 nm, while no clay platelets were located in the PVDF phase and in the PA11 nanodomains with the size of smaller than 200 nm. Moreover, the addition of organoclay shows significant effects on the phase structure of PVDF/PA11 blends.

Supermolecular structure variety of PMP membranes

Thermogravimetry was applied in order to study the variety of the phase structure of poly(4-methyl-1-pentene) (PMP) membranes. The results gave indirect information about the morphology of the polymeric systems. DTG curves, recorded for the membranes including residual amount of solvent, exhibited three processes. The processes were interpreted as a removal of the solvent molecules occluded in different local structures: ‘real’ amorphous; ‘semi-ordered’ amorphous, crystalline. The location of the molecules in those structures was correlated with chain behaviours studied using dynamic mechanical analysis. The relaxation processes (αg, αc) were analysed with a special attention to the amount of occluded solvent molecules.

Effects of molecular weight on phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

AbstractThe phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends was studied in relation to the molecular weight. The samples were prepared by both solution blends, which showed two glass‐transition temperatures (Tg), and melt blends (MQ), which showed a single Tg, depending on the composition of the blends. The Tg of the MQ series was independent of the molecular weight of the homopolymer, although the degree of transesterification in the blends was affected by the molecular weight. The MQ series showed two exotherms during the heating process of a differential scanning calorimetry scan. The peak temperature and the heat flow of the exotherms were affected by the molecular weight of the homopolymers. The strain‐induced crystallization of the MQ series suggested the independent crystallization of PET and PEN. Based on the results, a microdomain structure of each homopolymer was suggested. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2428–2438, 2005

Miscibility and morphology of chiral semicrystalline poly‐(R)‐(3‐hydroxybutyrate)/chitosan and poly‐(R)‐(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/chitosan blends studied with DSC, 1H T1 and T1ρ CRAMPS

AbstractThe phase structure of poly‐(R)‐(3‐hydroxybutyrate) (PHB)/chitosan and poly‐(R)‐(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (P(HB‐co‐HV))/chitosan blends were studied with 1H CRAMPS (combined rotation and multiple pulse spectroscopy). 1H T1 was measured with a modified BR24 sequence that yielded an intensity decay to zero mode rather than the traditional inversion‐recovery mode. 1H T1ρ was measured with a 40‐kHz spin‐lock pulse inserted between the initial 90° pulse and the BR24 pulse train. The chemical shift scale is referenced to the methyl group of PHB as 1.27 ppm relative to tetramethylsilane (TMS) based on 1H liquid NMR of PHB. Single exponential T1 decay is observed for the β‐hydrogen of PHB or P(HB‐co‐HV) at 5.4 ppm and for the chitosan at 3.7 ppm. T1 values of the blends are either faster than or intermediate to those of the plain polymers. The T1ρ decay of β‐hydrogen is bi‐exponential. The slow T1ρ decay component is interpreted as the crystalline phase of PHB or P(HB‐co‐HV). The degree of crystallinity decreases with increasing wt % of chitosan in the blend. The fast T1ρ of β‐hydrogen and the T1ρ of chitosan in the blends either follow the same trend as or faster than the weight‐averaged values based on the T1ρ of the plain polymers. Together with the observation by differential scanning calorimeter (DSC) of a melting point depression and one effective glass transition temperature in the blends, the experimental evidence strongly suggests that chitosan is miscible with either PHB or P(HB‐co‐HV) at all compositions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1253–1258, 2002

Miscibility, crystallization and phase structure of poly(3-hydroxybutyrate)/cellulose acetate butyrate blends

Blends of poly(3-hydroxybutyrate) (PHB) with cellulose acetate butyrate (CAB) were prepared by solution casting from chloroform solutions at different compositions. The miscibility, crystallization behavior and phase structure were investigated using differential scanning calorimetry, optical microscopy and small-angle X-ray scattering (SAXS). CAB/PHB blends were found to be miscible in the melt state as evidenced by the deduction of a single glass transition ( T g) for each composition, a depression in the equilibrium melting point of PHB, and a marked reduction in the spherulites growth rate of PHB in the PHB/CAB blends. The Flory–Huggins interaction parameter ( χ 12), obtained from melting point depression data, is composition dependent, and its value is always negative. The nucleation factor, K g, was determined using Lauritzen–Hoffman model. The K g values for the PHB in the blends are considerably lower than the K g value in the pure homopolymer. The phase structure of the blend in the solid state as revealed by SAXS is characterized by the presence of a homogeneous amorphous phase situated mainly in the interlamellar regions of crystalline PHB and consisting of CAB molecules and uncrystalline PHB chains.

Phase Structure of Poly(3-hydroxy butyrate)/Poly(vinyl acetate) Blends Probed by Small-Angle X-ray Scattering

The semicrystalline morphology of poly(3-hydroxy butyrate) (PHB)/poly(vinyl acetate) (PVAc) blends at four crystallization temperatures (Tc = 70, 90, 110, and 125 °C) was probed by small-angle X-ray scattering (SAXS). Morphological parameters including the crystal thickness (lc) and the amorphous layer thickness (la) were deduced from the interphase distribution function. Blending with PVAc thickened the PHB crystals. The amorphous layers were also swollen upon blending, but la displayed a maximum in its variation with PVAc composition. A zero-angle scattering was observed in the Lorentz-corrected SAXS profiles of PHB/PVAc 60/40 blend crystallized at 110 and 125 °C and 50/50 composition crystallized at 90−125 °C. Such a zero-angle scattering was attributed to the presences of amorphous domains between the lamellar stacks so as to generate gaps in the sequential stacking of lamellae. These amorphous domains were generated by the interfibrillar segregation of PVAc, where PVAc was expelled beyond several lay...

Modulated differential scanning calorimetry: 13. Analysis of morphology of poly(ethyl methacrylate)/polyurethane interpenetrating polymer networks

The phase structure of poly(ethyl methacrylate)–polyurethane (PEMA/PUR) interpenetrating polymer networks (IPNs) has been investigated by means of modulated-temperature differential scanning calorimetry (M-TDSC), dynamic mechanical thermal analysis (DMTA) and small-angle X-ray scattering (SAXS). Experimental data from both M-TDSC and SAXS indicate that the morphologies of all the PEMA/PUR IPN samples (90 : 10 to 10 : 90 PUR/PEMA) are multi-phase structures. The scattering peaks from SAXS are quite broad, thereby indicating a distribution of microdomain sizes from 5 to 12 nm. This structure formation in IPNs is a competitive process between phase separation and the formation of cross-links which restricts segmental diffusion. An M-TDSC-based characterization method for IPNs has been developed using the differential of heat capacity signal, d C p/d T, to analyze phase structure and calculate the weight fraction of each component.

Phase Structure of Poly(dimethylsiloxane−urea−urethane)- Segmented Copolymers as Observed by Solid-State Nuclear Magnetic Resonance Spectra

Three segmented copolymers having as hard segments poly(urethane−urea)s based on isophorone diisocyanate (IP) and 1,4-benzenedimethanol (B) and having as soft segments poly(dimethylsiloxane)s (PDMS) of three different molecular weights are analyzed by CP-MAS 13C-NMR. Comparison of cross-polarized and non-cross-polarized spectra, together with proton relaxation measurements, establishes the presence of separated phases and differences in their mobility. The T1ρ(H)'s and static 1H-NMR half-height line widths of PDMSyK−IP−B2 (y = 2.4, 10, and 27; refers to the PDMS molecular weight) give information about the motion as a function of the molecular weight of PDMS. A dipolar filter sequence is employed to estimate the size of the dispersed hard phases, which appears to be of about 5 nm for all samples. The overall (soft and hard) domain sizes increase with the increase of silicone molecular weights, as expected.

Phase structure of poly(vinyl alcohol) single crystals as revealed by high-resolution solid-state 13C n.m.r. spectroscopy

The phase structure composed of the crystalline and non-crystalline phases, in particular the structure of the non-crystalline phase and hydrogen bonding, has been examined for poly(vinyl alcohol) (PVA) single crystals with different molecular weights by cross-polarization/magic angle spinning 13C n.m.r., differential scanning calorimetry and X-ray measurements. Although the molecular weight is vigorously decreased for the single crystals conventionally prepared from triethylene glycol solution, no reduction in molecular weight occurs when they are crystallized in a triethylene glycol/glycerol mixed solvent after dissolution at relatively low temperatures. According to the method previously reported, the triplets of the CH resonance lines of the crystalline and non-crystalline components have been analysed to obtain information about the intramolecular and intermolecular hydrogen bonds. It is found that the probability of formation of intramolecular hydrogen bonds in the meso sequence greatly differs between the crystalline and non-crystalline components, slightly or insignificantly depending on the molecular weight and the crystallization condition. It is finally concluded that PVA single crystals are composed of a crystalline phase with a thickness of about 8.0 nm and a non-crystalline overlayer with a thickness of about 2.0 nm. Moreover, the non-crystalline overlayer should consist of short loops with rather restricted molecular mobility compared to the mobility of the amorphous component.

Phase structure of poly(oxyethylene) surfactants in water studied by fluorescence quenching

Binary systems of water and nonionic surfactants of the dodecyl poly(oxyethylene) type, C 12 H 25 -(OCH 2 - CH 2 ) m OH (C 12 E m ), have been studied by time-resolved fluorescence quenching (TRFQ). The interest has been focused on the diffusion-influenced quenching in liquid crystalline phases of the C 12 E 4 , C 12 E 5 , C 12 E 6 , and C 12 E 8 systems and the ability of the TRFQ method to discriminate between different quenching geometries. The relative diffusion coefficients of pyrene and 3,4-dimethylbenzophenone have been measured in rod-shaped and lamellar aggregates in aqueous solutions as well as in neat surfactants

Phase structure of poly(styrene-co-acrylic acid)/poly(ethylene oxide) blends by spin-label EPR and DSC

Blends of styrene-acrylic acid random copolymers (P(S-AA)) with poly(ethylene oxide) (PEO) have been studied. The copolymers contained up to 25 mol% AA monomers and the blends contained up to 60 wt% PEO. The presence of crystalline PEO in the blends is detected by DSC and verified by WAXS. EPR and DSC data indicate that pure polystyrene and PEO are immiscible in the temperature range 300-420K. The presence of two amorphous phases is detected for some blends based on a copolymer containing 5 mol% AA. The miscibility of the two components in the blends increases with increasing AA content of the copolymer.