The effect of the microstructure on the phase behavior of mixtures of polybutadiene (PB) and poly(ethylene-co-1-butene) (PEB) with polystyrene (PS) has been investigated. A series of PBs with 1,2-addition content ranging from 7 to 93% were synthesized by anionic polymerization, and a portion of each was subsequently hydrogenated to yield PEB. Polymer pairs with blend compositions from 10 to 90 wt % were cast from toluene for each of the 16 PS/PB pairs and 7 PS/PEB pairs. Laser light scattering was used to obtain cloud point measurements, which were then used to construct phase diagrams. It was found that, for constituent components with equivalent degrees of polymerization, PS/PEB pairs give rise to higher upper critical solution temperatures than PS/PB pairs, indicating that PS/PEB pairs are less miscible than PS/PB pairs. Experimental phase diagrams were curve-fitted to theoretical phase diagrams predicted from the Flory−Huggins theory with the expression for the interaction parameter α:  α = a + b/T + cφPS/T, where α is related to the Flory−Huggins interaction parameter χ by χ = αV r, where V r is the molar reference volume, T is the absolute temperature, and φPS is the volume fraction of PS in the mixture. α values for PS/PB mixtures increase with increasing 1,2-addition (miscibility decreases) while α values for PS/PEB mixtures decrease (miscibility increases) with increasing 1-butene content. Using these α values, the Helfand−Wasserman theory was applied to predict the order−disorder transition temperatures of PS-block-PB and PS-block-PEB copolymers with varying 1,2-addition and 1-butene content, respectively.

This work documents the development of the title system wherein the first dimension is a separation of polyolefins, according to composition, via an adsorption mechanism on a HYPERCARB stationary phase, and the second dimension is a separation of polyolefins on a gel permeation chromatography (GPC) column. Proper optimization of the experimental parameters including high temperature liquid chromatography (HTLC) flow rate, GPC flow rate, GPC column type, and solvent gradient program enabled successful operation of the two-dimensional (2D) system. Two angle light scattering at 90°and 15°and solution infrared absorbance detectors were used for qualitative and quantitative analysis of the 2D data. Apparent composition distribution, apparent molecular weight distribution, and the complete twodimensional (composition  molecular weight) distribution were obtained for a given polymer. This system is an improvement over a prior two-dimensional system based on temperature rising elution fractionation (TREF)/GPC in that TREF has difficulty separating polyolefins by composition if the polyolefins contain more than approximately 8 mol percent comonomer. Polyolefins synthesized from different catalysts (Metallocene and Ziegler-Natta) showed differences in the molecular weight, composition and number of resolved species in their respective 2D HTLC-GPC chromatograms as a function of catalyst type. Although the polymers studied here were all polyolefins, this approach can also be extended to other polymers.

Fully saturated hydrocarbon polymers often exhibit superior stability toward thermal, oxidative, and radiation-induced degradation. Recent improvements in catalyst technology allow for the convenient synthesis of the saturated hydrocarbon poly(cyclohexylethylene) (PCHE) from polystyrene (PS) by heterogeneous catalytic hydrogenation. The focus of this report was to prepare nearly monodisperse samples of polystyrene by anionic polymerization and to fully saturate those materials by catalytic hydrogenation. The thermal and viscoelastic properties of these materials were then evaluated using differential scanning calorimetry and dynamic mechanical spectroscopy. On the basis of these experimental results, the glass transition temperature of PCHE has been found to approach 148 °C at high molecular weight. Relationships between the zero shear viscosity, steady-state compliance, and rubbery plateau modulus of PCHE with respect to molecular weight have been determined, and entanglement spacing and packing length have been calculated from these data. PCHE shows an entanglement spacing (M e) of 40 200 g/mol, compared to 18 700 g/mol for the starting material PS. This increase in glass transition temperature and entanglement length can be attributed to the increase in steric bulk of the cyclohexyl substituent compared to the phenyl ring present in the starting material.

Anionic and nitroxide-mediated (NM) radical polymerization works well for styrene but not for acrylates. We have overcome this problem and successfully prepared styrene-b-n-butyl acrylate (S-BA), styrene-b-methyl methacrylate (S-MMA), styrene-b-isoprene (S-IP), and styrene-alt-acrylonitrile-b-isoprene (SAN-IP) polymers using a sequential normal/living radical polymerization scheme. Clear (S-IP and SAN-IP) to translucent (S-BA and S-MMA) films were obtained having microphase-separated polymer morphology. GPC studies and chemical digestion of the IP segments of S-IP and SAN-IP block copolymers confirmed their block structure. The sequential normal/living radical polymerization approach provides a new route to synthesize block polymers that have previously proven very difficult to make.

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