Phase Behavior of Polystyrene/Polybutadiene and Polystyrene/Hydrogenated Polybutadiene Mixtures:  Effect of the Microstructure of Polybutadiene

Abstract

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.

Thermodynamic interactions in blends of poly(4‐tert‐butyl styrene) and polyisoprene by small‐angle neutron scattering

“…Although extensive studies of isotopic blends,1, 2 polyolefin blends,3–9 and polydiene blends10–14 has furthered the understanding of the thermodynamics of mixing of polymers and provided data for testing theoretical approaches,15, 16 a number of outstanding issues still persist. One of these is the attempt to bridge between different families of polymers, that is, to understand the mixing of polyolefins with polydienes,17 polyolefins with styrenics,18 and polydienes with styrenics 19…”

Development of Elastomers Based on Fully Hydrogenated Styrene–Diene Block Copolymers

“…For blends of polystyrene (PS) and hydrogenated polybutadiene (polyethylene-co-1-butene, or PEB), studies of cloud-point behavior showed that the level of phase segregation decreases with increasing 1-butene content [17]. This trend has also been observed for PCHE/PEB blends [20], where PCHE denotes fully hydrogenated PS, which we designate poly(cyclohexylethylene).…”

“…Polybutadiene segment microstructure was modified by the addition of dry tetrahydrofuran (THF) at varying concentrations. Polymerization in cyclohexane provided polybutadiene with about 8 % vinyl repeat units, and samples with up to 60 % vinyl content could be prepared using the cosolvent THF [3,17]. The melt viscosity of the final polymer was assessed by performing melt flow rate measurements according to a standard test method protocol [27] with a 5 kg weight at 235 8C; values are given in units of grams polymer per ten minute increment.…”

Epifluorescence studies and secondary relaxation processes in immiscible blends of polybutadiene‐poly(2‐vinyl naphthalene) by fluorescence spectroscopy

“…This polymer (P2VN) is chosen instead of PS because of its higher fluorescence quantum yield,9, 10 which allows easier observation of the morphology using a conventional epifluorescence microscope. As an analogue of PS, blends of P2VN with PB should also be immiscible with an upper critical solution temperature and we thus assume that the morphological properties might also be similar and that the results produced in this work can be transferred to the other polymeric system 27–32. In addition, because the morphology of the PB/PS blend is also controlled by the PB microstructure, PB with a high content of 1‐2‐trans addition was chosen in the present work 30…”