Microscopic Fourier Transform Infrared Characterization on Two Types of Spherulite with Polymorphic Crystals in Poly(heptamethylene terephthalate)

Abstract

FTIR microspectrometry with in situ temperature variation and IR-peak-mapping capability, and POM characterization were used to study the crystal distribution in dual spherulites in poly(heptamethylene terephthalate). By tracing the crystalline IR bands of the α-crystal and β-crystal to get the crystal distribution, the techniques resolve that the ringed and ringless spherulites comprise α- and β-crystals, respectively. In addition, temperature-dependent IR analyses on the spots related to the two crystals also reveal the α- and β-crystals melt at 98 and 104 °C, respectively. The ringed and ringless spherulites were proven to be correlated with the α- and β-crystal forms, respectively.

Catalyst-Free Single-Step Solution Polycondensation of Polyesters: Toward High Molar Masses and Control over the Molar Mass Range

“…Using DSC, we were able to clearly demonstrate the melt recrystallization behavior of PATs. Previous reports have described multiple melting peaks for some PATs, suggesting the presence of either crystal lamellae with varying thickness and/or polymorphism (i.e., different crystalline phases). ,,,,− However, to the best of our knowledge, no research has been able to prove the simultaneous crystallization during the melting endotherm(s) in a direct way and under nonisothermal conditions for all PATs. In regular DSC experiments, a small exotherm before the melting peak was observed for some PATs (i.e., PAT ( n = 5) and PAT ( n = 7) ), indicating this melt recrystallization phenomenon.…”

Dendritic Morphology Composed of Stacked Single Crystals in Poly(ethylene succinate) Melt-Crystallized with Poly(p-vinyl phenol)

“…High polymers, for example, hydrocarbons such polyethylene, polypropylene, polyisobutylene, poly(butene-1), iso-poly(4-methylpentene-1), and polystyrene, crystallize to form spherulite. Some polyesters also form spherulite such as poly(ethylene terephthalate), poly(heptamethylene terephthalate), , poly(octamethylene terephthalate), poly(nonamethylene terephthalate), − poly(R-3-hydroxyvalerate), poly(R-3-hydroxybutyrate), poly(lactic acid), poly(vinylidene fluoride), etc. In reverse, dendritic crystallization has been reported for a number of polymers, polymer blends, or copolymers, melt-crystallized in ultrathin films, including polyethylene (PE), isotactic polystyrene (iPS), − poly(ethylene oxide) (PEO), poly(caprolactone), , poly-2-vinylpyridine-poly(ethylene oxide) (P 2 VP-PEO) block copolymers, and poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends. − All these studies showed that the dendritic crystals were formed in the samples with the film thickness of below 150 nm.…”

From Nano-Crystals to Periodically Aggregated Assembly in Arylate Polyesters—Continuous Helicoid or Discrete Cross-Hatch Grating?

“…Aryl polyesters may possess polymorphism; however, monomorphism or not in the crystal-unit lattices usually cannot be correlated with the formation of multiple types of spherulites. Monomorphic poly(octamethylene terephthalate) (POT) displays multiple types of spherulites; poly(heptamethylene terephthalate) (PHepT) can possess fractions of α and β crystal lattices and can exhibit many different spherulite patterns with peculiarly varying periodicity [ 18 ]. Although commercially available PTT has been widely investigated [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ], arylate polyesters and their crystal morphologies have been less probed [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ].…”