Poly , blend sample with

A solid-state C NMR study of the intermolecular hydrogen bonding formation in a blend of phenolic resin and poly(hydroxyl ether) of bisphenol A was reported by Wu et at) " The presence of a single glass transition temperature for all of the blend samples with different composition as disclosed by the DSC measurements demonstrates that the blends are thermodynamically miscible. The solid state NMR parameters, including chemical shift, efficiency of cross-polarization and Ti, confirm the presence of more free OH groups when one of the polymers is the minor component. 

Some grafting between polystyrene and polyethylene may occur, but we think not. Substantial amounts of polystyrene (but not all) have been extracted from the blend samples by soaking the specimens in refluxing THF for several days. We suspect that if grafting does occur, it is not a significant contributor to polystyrene mass uptake. All the polystyrene could be extracted from a 50 wt % polystyrene/poly(4-methyl-l-pentene) (PMP) blend that was prepared by essentially the same procedure. The backbone of PMP (with two tertiary C —H bonds per repeat unit) is likely more susceptible to radical grafting than HDPE. 

Nguyen and Kausch [1984] found that the presence of phenyl groups in poly(styrene-co-acrylo-nitrile), SAN, protects PMMA in the blend, during radiolysis (Table 11.9). SAN and PMMA were dissolved in dimethyl formamide, 50- J,m-thick films were cast, and then dried under vacuum. Transparent bar specimens were compression-molded from the film. Mixing the polymers by co-precipitation from methanol resulted in opaque samples. Gamma irradiations were done in evacuated and sealed glass tubes, at a dose rate of 3 kGy/h. Comparison of freshly irradiated samples with irradiated and annealed ones showed the absence of any post-irradiation effects. 

Storage modulus curves for polystyrene (PS)/poly(dlmethyl siloxane) (PDMS) films (a) without and (b) with 1.0 wt% cyclodextrin (CD) core. The solid lines represented samples with no PDMS. The initial and retained amounts of PDMS are shown in the insets for the other samples. (Reproduced from Busche, B. Tonelli, A. E., and Balik, C. M. 2010. Properties of polystyrene/poly(dimethyl siloxane) blends partially compatibiUzed with star polymers containing a y-cyclodextrin core and polystyrene arms. Polymer 51 6013-6020 with permission from Elsevier.)... 

Test of time-temperature superposability for the modulus Gpigs of poly(p-tert butyl styrene) (PtBS) components in the polyisoprene (PI)/PtBS miscible blends (w i = 56 wt%) as indicated. The sample code numbers of the blends denote 10" M of the components. Gp,gs were obtained by subtraction of the PI modulus from the blend modulus. The reference temperature is T, = 20°C for the two blends. (Redrawn, with permission, from Chen, Q., Y. Matsumiya, Y. Masubuchi, H. Watanabe, and T. Inoue. 2011. Dynamics of polyisoprene-poly(p-ferf-butylstyrene) diblock copolymer in disordered state. Macromolecules 44 1585-1602.)... 

It was reported recently, that polymeric can also form quasicrystals. Hayashida et al. [50] demonstrated that certain blends of polyisoprene, polystyrene, and poly(2-vinylpyridine) form starshaped copolymers that assemble into quaskrystals. By probing the samples with transmission electron microscopy and X-ray diffraction methods, they conclude that the films are composed of periodic patterns of triangles and squares that exhibit 12-fold symmetry. These are signs of quasicrystalline ordering. Such ordering differ from conventional crystals lack of periodic structures yet are well-ordered, as indicated by the sharp diffraction patterns they generate. Quasi-crystals also differ from ordinary crystals in another fundamental way. They exhibit rotational symmetries (often five or tenfold). There are still some basic questions about their stracture. 

Photomicrographs of these compositions at the 25% resin concentration confirm the incompatibility of polystyrene and the compatibility of poly(vinyl cyclohexane) with natural rubber. These are shown in Pigs. 3 and 4. A dispersed resin about 2-4y in size, phase is clearly seen in the polystyrene example, while the blend containing poly(vinyl cyclohexane) has no visible structure within the limits of resolution of the equipment. The circles in the center of Fig. 4 are artifacts resulting from preparation of the sample for microscopy. 

Systematic study of the mechanism of formation of the 3-D network in the case of polymer blends with H-bonding demonstrated that this process takes place in the melt before the drawing step, and the subsequent cold drawing results in drastic reduction of the diameters of the network elements. This conclusion was proved by SEM observation of melt blended samples taken immediately after the extruder die. They were treated with water in order to extract the PVA and analyzed by SEM. A blend of PVA with glycol-modified poly(ethylene terephthalate) (PETG) was used for these experiments. 

Fig. 2. 100 kHz dielectric loss spectra of polyimide -poly(ether-sulfone) blends, together with the spectra of the pure constituents, in the first heating run. Samples were solvent cast films. 

In a first set of measurements poly(styrene) samples differing in chain length were mixed with their brominated derivatives and the authors determined the maximum tolerable bromine content. A, for a 50/50 (w/w) blend to remain homogeneous, i.e., transparent. A was found to increase with decreasing chain length of the original poly (styrene). A second set concerned 50/50 mixtures of substituted Dolvfstvrenes) of different bromine content. Kambour et al. found that the maximum... 

SEM photomicrographs of the 70/30 PET/LDPE+diethyl maleate grafted ultra-low-density polyethylene (ULDPE-g-DEM) blends obtained with a mixing time of 20 min. (A) and (B) no copolymer, sample cut parallel to flow direction (C) no copolymer, sample cut perpendicular to flow direction. (From M. B. Coltelli, Catalysed Reactive Compatibilization of Polyolefin and Poly(ethyIene terephthalate) Blends Reactions Mechanisms and Phase Morphology Development, Ph.D. thesis. University of Pisa, Italy, 2005.)... 

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