Molecular motion blends Poly

Radioluminescence spectroscopy has been used to examine molecular motion, solubility, and morphology of heterogeneous polymer blends and block copolymers. The molecular processes involved in the origin of luminescence are described for simple blends and for complicated systems with interphases. A relatively miscible blend of polybutadiene (PBD) and poly(butadiene-co-styrene) and an immiscible blend of PBD and EPDM are examined. Selective tagging of one of the polymers with chromophores in combination with a spectral analysis of the light given off at the luminescence maxima gives quantitative information on the solubility of the blend components in each other. Finally, it is possible to substantiate the existence and to measure the volume contribution of an interphase in sty-rene-butadiene-styrene block copolymers. 

The objective of this investigation is to describe the effect of physical aging on the molecular motion of the membranes of PMSP and poly(l-trimethyl-l-propyne-co-1-phenyl-1-propyne) [poly(TMSP-co-PP] and blend polymer of PMSP with poly(l-phenyl-1-propyne) (PPP). 

Effect of aging on the permeability and molecular motion of the membranes of PMSP, poly(TMSP-co-PP) and blend of PMSP/PPP Glassy polymers, such as PMSP, are nonequilibiium materials and their permeation and sorption properties drift over time as thermally driven, small-scale polymer segmental motions cause a relaxation of nonequilibrium excess free volume. The microcavities of large size which are present in PMSP membrane have been considered to be responsible for the decay of C h and the gas permeability (4). Therefore, it is possible to stabilize the gas permeability by control the C by copolymerization or blending with the other acetylene derivatives such as PP and PPP, respectively. 

The interactions between two polymers could limit the free-radical decay after irradiation. Miklesova and Szocs carried out y-irradiation of miscible poly(methylmethacrylate) (PMMA)/polyefhyleneoxyde (PEO) blends at liquid N2 temperature with a total dose of 10 kGy The blends were prepared by mixing on a Brabender plasticorder during 6 or 12 min. The authors observed that the free-radical decay is slower when fhe fime of mixing is longer because the transfer of the radical center is controlled by molecular motions. These motions are affected when more interactions occur between both polymers and consequently the decay is slowed. 

Recent developments have been in the area of microthermal analysis using thermal conductivity with thermal diffiisivity signals or AFM to visualize specific areas or domains in the material and perform localized thermal analysis studies (183,184). Relaxational behavior over time and temperature is related to changes in free volume of the material. Positron annihilation lifetime spectroscopy (PALS) measurements of positron lifetimes and intensities are used to estimate both hole sizes and free volume within primarily amorphous phases of polymers. These data are used in measurement of thermal transitions (185,186) structural relaxation including molecular motions (187-189), and effects of additives (190), molecular weight variation (191), and degree of crystallinity (192). It has been used in combination with DSC to analyze the range of miscibility of polymethyl methacrylate poly(ethylene oxide) blends (193). 

Zhang, X.Q., Takegoshi, K, and HikichL K. (1991) Poly(vinylphenol)/poly(methyl acrylate) and poly(vinylphenol)/poly (methylmethacrylate) blends hydrogen bonding, miscibility, and blending eflfects on molecular motions as studied by CCP/MAS NMR. Macromolecules, 24, 5756-5762. 

Both cis-polyisoprene (PI) and poly(vinyl ethylene) (PVE) have the type-B dipoles perpendicular to the chain backbone, and PI also has the type-A dipoles parallel along the backbone (cf. Figure 3.2). The dielectric relaxation detects the fluctuation of these dipoles, as explained in Section 3.2.2. The fluctuation of the type-B dipoles is activated by the fast, local motion of the monomeric segments, which enables the dielectric investigation of this motion. In contrast, the slow dielectric relaxation of PI due to the type-A dipoles exclusively detects the fluctuation of the end-to-end-vector R (see Equation 3.23). These dielectric features of PI and PVE are clearly noted in Figure 3.11, where the e" data are shown for a PI/PVE blend with the component molecular weights Mp, = 1.2 x 1(P and Mpyp = 6 x 1(P and the PI content rvpi = 75 wt% (Hirose et al., 2003). The data measured at different temperatures are converted to the master curve after the time-temperature superposition with the reference temperature of T, = -20°C, as explained later in more detail. The three distinct dispersions seen at high, middle, and low... 

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