Crystal morphology and thermodynamics of poly(ethylene-4,4 '-biphenyl dicarboxylate) and related copolymers with ethylene-2,6-naphthalene dicarboxylate
J. Wendling et al., Crystal morphology and thermodynamics of poly(ethylene-4,4 '-biphenyl dicarboxylate) and related copolymers with ethylene-2,6-naphthalene dicarboxylate, MACROMOLEC, 32(23), 1999, pp. 7866-7878
We present a detailed experimental and modeling investigation of poly(ethyl
ene-4,4'-biphenyl dicarboxylate) (PEBB) and the related random copolymers p
oly(ethylene-4,4'-biphenyldicarboxylate-co-2,6-naphthalene dicarboxylate) (
PEBB/EN). We find that different polymorphs exist for the PEBB homopolymer
and suggest a second crystal unit cell, different from that which is discus
sed in the Literature. PEBB/EN copolymers, which are shown here to be rando
m copolymers, are found to be semicrystalline for all naphthanoate concentr
ations. By combination of DSC, X-ray, and solid-state NMR experiments, unif
orm comonomer inclusion is proposed for copolymers containing a high amount
of EN; for low EN concentrations, these comonomers are rejected from the c
rystals. By comparison of the comonomer inclusion Gibbs energy, which was e
stimated from experiments, to those obtained from thermodynamic integration
calculations, it was found that PEBB/EN copolymers are able to cocrystalli
ze by aggregation of like and by segregation of unlike repeat units. Once t
hese comonomer inclusions have reached a considerable size, the average def
ect Gibbs energy reduces to the thermal energy.