Crystalline isomeric polyester block copolymers. Scanning calorimetry and density measurements

Abstract

SynopsisA series of isomeric polyester block copolymers were synthesized by coupling hydroxyl-terminated poly(hexamethy1enesebacate) (HMS) and poly(2-methyl-2-ethy1-1,3-propylene sebacate) (MEPS) with hexamethylene diisocyanate. Poly(HMS) is crystalline, whereas poly(MEPS) is amorphous. AU of the block copolymers, including one containing only 28% HMS were found to crystallize. DSC, density, and optical microscopy were used to measure the thermal transition temperatures and the degree of crystallinity. The data indicate that block copolymerization causes a small depression in the melting point and that the degree of crystallinity of the HMS block in the copolymer is more a function of molecular weight than it is of copolymer composition. Crystallization appears to be the major driving force for phase separation in this isomeric copolymer system.

Poly(ethylene glycol)-block-poly(butyl acrylate). II. Characterization and properties

“…It is obvious that volume filling spherulitic films are block copolymers. Contrary to the crystallinity of HMS-MEPS copolymers, 24 the crystallinity of formed and the volume of the PEO spherulites in block copolymers decreases. In the copolymer, the PEO-PBA block copolymers increases with the increase of the PEO content, and its value is relacrystallization of PEO sequences is impeded by amphous PBA sequences; consequently, the copoltively lower.…”

Morphology and properties of crystalline polyester‐siloxane block copolymers

“…ur recent studies on crystalline block copolymers 0 have focused on the morphology and compatibility of copolymers containing isomeric polyester segments, namely, crystallizable poly(hexamethy1ene sebacate) (H MS) and amorphous poly(2-methyl-2-ethyl-1,3propylene sebacate) (MEPS). Our results (1) indicate that these multiblock copolymers are compatible above the melting point of HMS, but in the solid state, they readily crystallize to form volume filling spherulitic structures. Crystallization appears to be the major driving force for phase separation in this system, and it likely has a major effect on the texture of the copolymers in the solid state.…”

“…Films of HMS homopolymer can be prepared by solvent coating or by cooling the polymer melt to the crystallization temperature. Typically, HMS films are spherulitic in texture and have melting points near 65°C and degrees of crystallinity in the range of 60-75 percent, depending on molecular weight (1).…”

Chain propagation/step propagation polymerization: synthesis of defect-free telechelomers

“…This equation has been used to calculate Tmobs of the poly(hexamethylene sebacate) segment due to block copolymerization with a poly-(dimethylsiloxane) segment. [28][29] In a previous study, we8 used eq 1 to calculate the upper and lower limits of the poly(pivalolactone) hard segment in their poly(oxyethylene-bZode-pivalolactone) telechelomers. The upper limit, with pH = I, equals TmH, and the lower limit was calculated using pH = Wh• The lower limit is the Tmobs expected if no microphase separation occurs, and the upper limit is the Tmoh* expected for complete microphase separation.…”