Direct evidence for transesterification and randomization in a mixture of homopolyesters of poly(4-hydroxybenzoic acid) and poly(6-hydroxy-2-naphthoic acid) above 450.degree.

Mühlebach, Andreas; Economy, James; Johnson, R. D.; Karis, T. E.; Lyerla, J. R.

doi:10.1021/ma00208a041

Cited by 57 publications

(33 citation statements)

References 5 publications

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“…This concept was proposed first by Lenz et a1.3639) and was subject to criticism in the first publications on this issue by Economy et al 40). Porter'') also indicated that the effect observed by Lenz can be explained without assuming chemical interactions.…”

Section: Discussionmentioning

confidence: 97%

Sequential reordering in condensation copolymers, 2. Melting‐ and crystallization‐induced sequential reordering in miscible poly(butylene terephthalate)/polyarylate blends

Denchev¹,

Sarkissova²,

Fakirov³

et al. 1996

Macro Chemistry & Physics

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A 50/50 (weight ratio (38/62 mole ratio referred to repeating units)) blend of poly(butylene terephthalate) (PBT) and polyarylate (PAr), was studied by means of thermal, solubility, X-ray and nuclear magnetic resonance techniques after annealing procedures that enable transesterification. Prolonged thermal treatment at 290 "C gives rise to a copolymer that no longer reveals melting or crystallization. In accordance with previous reports, this effect is attributed to the formation of a random copolymer. Additional annealing of such samples at the relatively low temperature of 140°C results in the reappearance of melting endotherms in the differential scanning calorimetry curves. This effect is explained by crystallization-induced sequential reordering from random to block copolymer by means of transreactions. In that way a PBTPAr blend was shown to be another polymer system, along with poly(ethy1ene terephthalate) (PET)/polycarbonate (PC) and PETPAr blends, in which the entire cycle is realized, from two homopolymers via a block-and random copolymer to a block copolymer. The unusually low temperature at which the crystallization-induced sequential reordering to block polymers takes place is explained by the miscibility of PBT and PAr which enables transreactions to take place in the bulk.

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Section: Discussionmentioning

confidence: 97%

Sequential reordering in condensation copolymers, 2. Melting‐ and crystallization‐induced sequential reordering in miscible poly(butylene terephthalate)/polyarylate blends

Denchev¹,

Sarkissova²,

Fakirov³

et al. 1996

Macro Chemistry & Physics

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show abstract

“…Structural randomization has been reported, for instance, in blends of PBT and bisphenol-A polycarbonate, 100 of PBT and aromatic polyesters, 101 of poly(ethylene adipate) and poly(trimethylene adipate), 102 and of poly(6-hydroxy-2-naphthoic acid) and poly(4-hydroxybenzoic acid). 103 Similarly, aliphatic polyester-aromatic polyester block copolymers undergo randomization during melt processing and, for this reason, have not found any commercial applications as thermoplastic elastomers, unlike polyesterurethanes or polyesterethers.…”

Section: Interchange Reactionsmentioning

confidence: 99%

Polyesters

Fradet

Tessier

2003

Synthetic Methods in Step‐Growth Polymers

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“…potentially be beneficial if understood and controlled or can be the origin of mechanical instabilities under processing conditions [2,3].…”

mentioning

confidence: 99%

Simulations of liquid crystals in Poiseuille flow

Denniston

Orlandini

Yeomans

2001

Computational and Theoretical Polymer Science

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Lattice Boltzmann simulations are used to explore the behavior of liquid crystals subject to Poiseuille flow. In the nematic regime at low shear rates we find two possible steady state configurations of the director field. The selected state depends on both the shear rate and the history of the sample.For both director configurations there is clear evidence of shear-thinning, a decrease in the viscosity with increasing shear rate. Moreover, at very high shear rates or when the order parameter is large, the system transforms to a log-rolling state with boundary layers that may exhibit oscillatory behavior.

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Direct evidence for transesterification and randomization in a mixture of homopolyesters of poly(4-hydroxybenzoic acid) and poly(6-hydroxy-2-naphthoic acid) above 450.degree.

Cited by 57 publications

References 5 publications

Sequential reordering in condensation copolymers, 2. Melting‐ and crystallization‐induced sequential reordering in miscible poly(butylene terephthalate)/polyarylate blends

Sequential reordering in condensation copolymers, 2. Melting‐ and crystallization‐induced sequential reordering in miscible poly(butylene terephthalate)/polyarylate blends

Polyesters

Simulations of liquid crystals in Poiseuille flow

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