Polymer Fractionation at a Lower Critical Solution Temperature Phase Boundary

1967 ◽  
Vol 40 (5) ◽  
pp. 1544-1552
Author(s):  
C. H. Baker ◽  
C. S. Clemson ◽  
G. Allen
Keyword(s):  
Molecular Weight ◽  
Phase Boundary ◽  
Lower Critical Solution Temperature ◽  
Solution Temperature ◽  
Temperature Phase ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature ◽  
Two Samples ◽  
Polymer Fractionation ◽  
Molecular Weight Fractions

Abstract The influence of pressure on a lower critical solution temperature is much more pronounced than on an upper critical solution temperature. Accordingly it is possible to control phase separation at a LCST phase boundary under isothermal conditions by merely adjusting the pressure on the system. An apparatus has been constructed to investigate the isothermal fractionation of polyisobutene in which precipitation is controlled by pressure. Two samples of polyisobutene of Mv=1.76×106 and 9.0×104 have been fractionated in isopentane solution so as to yield up to six and nine fractions respectively. The integral molecular weight distribution curves thus obtained are compared with those obtained from conventional fractionations at an UCST. The sensitivity of the method is poor with regard to the separation of low molecular weight fractions and degradation occurs at the higher temperatures to an appreciable extent.

scholarly journals Effect of Hydrophobic Interactions on Lower Critical Solution Temperature for Poly(N-isopropylacrylamide-co-dopamine Methacrylamide) Copolymers

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 991 ◽  
Author(s):  
Alberto García-Peñas ◽  
Chandra Sekhar Biswas ◽  
Weijun Liang ◽  
Yu Wang ◽  
Pianpian Yang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Lower Critical Solution Temperature ◽  
Hydrophobic Interactions ◽  
Structural Information ◽  
Drug Carriers ◽  
Solution Temperature ◽  
Polymerization Degree ◽  
Tissue Engineering Scaffolds ◽  
Critical Solution Temperature ◽  
Precise Control

For the preparation of thermoresponsive copolymers, for e.g., tissue engineering scaffolds or drug carriers, a precise control of the synthesis parameters to set the lower critical solution temperature (LCST) is required. However, the correlations between molecular parameters and LCST are partially unknown and, furthermore, LCST is defined as an exact temperature, which oversimplifies the real situation. Here, random N-isopropylacrylamide (NIPAM)/dopamine methacrylamide (DMA) copolymers were prepared under a systematical variation of molecular weight and comonomer amount and their LCST in water studied by calorimetry, turbidimetry, and rheology. Structural information was deduced from observed transitions clarifying the contributions of molecular weight, comonomer content, end-group effect or polymerization degree on LCST, which were then statistically modeled. This proved that the LCST can be predicted through molecular structure and conditions of the solutions. While the hydrophobic DMA lowers the LCST especially the onset, polymerization degree has an important but smaller influence over all the whole LCST range.

scholarly journals Lower Critical Solution Temperature Phase Behavior of Natural Rubber/Polybutadiene Blend

2002 ◽  
Vol 34 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Seiichi Kawahara ◽  
Yasuhiro Asada ◽  
Yoshinobu Isono ◽  
Kiyoshige Muraoka ◽  
Yasuhisa Minagawa
Keyword(s):  
Natural Rubber ◽  
Phase Behavior ◽  
Lower Critical Solution Temperature ◽  
Solution Temperature ◽  
Temperature Phase ◽  
Critical Solution Temperature

Development Of Miscible Blends From Intrapolymer Repulsive Interactions: Polycarbonate/Polystyrene Ionomers

1996 ◽  
Vol 461 ◽  
Author(s):  
R. Xie ◽  
R. A. Weiss
Keyword(s):  
Molecular Weight ◽  
Weak Interactions ◽  
Solution Temperature ◽  
Strong Interactions ◽  
Sulfonated Polystyrene ◽  
Bisphenol A Polycarbonate ◽  
Critical Solution Temperature ◽  
Miscible Blends ◽  
Upper Critical Solution Temperature ◽  
Repulsive Interactions

ABSTRACTThe phase behavior of blends of zinc sulfonated polystyrene (ZnSPS) and bisphenol-A polycarbonate (PC) was studied as a function of the sulfonation level and the molecular weight of the ZnSPS ionomer. The system exhibits upper critical solution temperature (UCST) behavior. The cloud point temperatures increased with increasing ZnSPS molecular weight and decreased with increasing sulfonation level. No strong interactions between ZnSPS and PC were detected by FTIR. The composition dependence of the glass transition temperatures of the miscible blends exhibited negative deviation from linear additi vity, which is consistent with no or weak interactions between ZnSPS and PC. Miscibility is believed to arise from strong repulsive interactions between the charged and uncharged species on the ionomer chain.

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