Chain rigidity temperature

High-strength and temperature-resistant polymers Styrene-butadiene-styrene, triblock polymer, thermoplastic elastomer Crystalline domains with rigid chains between them and cross-finking chains Rigid-chain domains in a flexible-chain matrix... 

Nanostructures primarily result from polyelectrolyte or interpolyelectrolyte complexes (PEC). The PEC (also referred to as symplex [23]) is formed by the electrostatic interaction of oppositely charged polyelectrolytes (PE) in solution. The formation of PEC is governed by physical and chemical characteristics of the precursors, the environment where they react, and the technique used to introduce the reactants. Thus, the strength and location of ionic sites, polymer chain rigidity and precursor geometries, pH, temperature, solvent type, ionic strength, mixing intensity and other controllable factors will affect the PEC product. Three different types of PEC have been prepared in water [40] (1) soluble PEC (2) colloidal PEC systems, and (3) two-phase systems of supernatant liquid and phase-separated PEC. These three systems are respectively characterized as ... 

Analysis of the sequence data obtained from various GAPDH and PGK molecules shows that adaptation to the higher temperature is accompanied by an increase of average hydrophobicity and a decrease of chain flexibility. Similar trends have also been deduced from comparisons of bacterial proteins adapted to different temperatures [17,18]. Although the difference in these parameters catmot be quantitatively correlated with changes in thermophilicity, nevertheless these trends are indicative of the importance of hydrophobic interactions and chain rigidity for the structure of thermophilic proteins. 

Symmetry also affects Tg. It might be expected that polyisobutylene, (—CH2 — C(CH3)2—) , would have a Tg greater than polypropylene, (—CH2 — CH(CH3)—) , as a consequence of the two —CH3 groups bonded to the backbone, which would tend to increase the chain rigidity. But this is not the case polyisobutylene is a rubber that has a Tg of —71°C, while polypropylene presents Tg = —23°C. Another example of how symmetry plays an important role in the Tg is seen if we compare poly (vinyl chloride) Tg = 81°C) and poly(vinylidene chloride) Tg = — 19°C) (31). As a general rule, it can be said that an increase in symmetry produces a decrease in the glass transition temperature. 

The purpose of this research is to synthesize a series of thermotropic liquid crystalline PECs consisting of HBA, DHBP, and carbonyl units with good melt processability and high heat deflection temperatures. The carbonate linkage is expected to reduce LCTT without reduction of the chain rigidity and heat resistance. 

Substituting max into the equation, we obtain the free energy which is a function of the nematic coupling a, the chain rigidity (l/lo) and the temperature T. The transition temperature can be obtained from the form of free energy. The form of free energy is rather complicated. We apply the Landau-de Gennes theory to analyze it. 

The experimental results suggest that, for these polylmides, the most flexible system had the lowest wear rate. Of the three polylmides tested, PIB should have the most flexible chain, as indicated by the glass transition temperature, because of the presence of the oxygen linking group. Chain rigidity is approximated... 

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