Reorganization of poly(ethylene terephthalate) structures and conformations to alter properties

Abstract

The solid-state morphologies, structures, and chain conformations of poly (ethylene terephthalate) (PET) have been reorganized/altered from those normally produced by solution and melt processing. This has been achieved by two distinct methods: (1) formation of a crystalline inclusion compound (IC) between guest PET and host c-cylodextrin (c-CD), followed by removal of the host c-CD and coalescence of the guest PET (c-PET) and (2) rapid precipitation of PET from a warm trifluoracetic acid solution into a large excess of rapidly stirred acetone (p-PET). Our prior observations (FTIR, NMR, DSC, X-ray) demonstrated that c-PET processed in this manner has a morphology, structure, and non-crystalline chain conformations that are quite distinct from those of as-received PET (asr-PET). Where possible to compare, here we find that c-and p-PETs behave very similarly, but very distinctly from asr-PET. The reorganized c-and p-PETs were found to be repeatedly rapidly crystallizable from the melt with a high level of crystallinity, and in their non-crystalline regions to have tightly packed chains predominantly adopting highly extended kink conformations, which evidence no glass-transition behavior. What is most unusual and somewhat puzzling is that their contrasting structures, morphologies, conformations, and thermal responses were observed to be independent of melt annealing, and persisted even after holding both samples above T m for extended periods (hours). p-PET, which can be produced in larger quantities than c-PET, was utilized to measure additional macroscopic properties, such as melt viscosities, densities, and the stressstrain and thermal shrinkage of melt-pressed films, for comparison to those of asr-PET. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: [735][736][737][738][739][740][741][742][743][744][745][746] 2007

Improving Poly(ethylene terephthalate) Through Self‐nucleation

“…Though not presented here, the FTIR spectra of asr‐ and p‐PETs are similar except for greater resolution in the p‐PET spectrum 4. Improved resolution was also seen for c‐PET3 and attributed to its high crystallinity and non‐crystalline regions consisting of chains pre‐dominantly in the gauche ± trans gauche ${\mp} $ conformations (see Figure 3), which guest PET chains in the channels of its precursor γ‐CD‐IC crystals are believed to adopt 3–5, 7. PET cast from TFA/chloroform solution exhibited an FTIR spectrum closely similar to that of asr‐PET 3…”

“…During the course of forming the PET‐γ‐CD‐IC,3 several control experiments were conducted. It was observed that PET rapidly precipitated (p‐PET) from a trifluoroacetic acid (TFA)/chloroform solution upon slow addition to rapidly stirred acetone (see Supporting Information) evidenced behavior closely similar to that of c‐PET 4, 5…”

“…The main aim of this research is to improve the properties of PET by using a simple precipitation method 3, 4. We are trying to generate a PET with novel morphologies and unique properties that will be easy to process with retention of all desirable and improved qualities.…”

“…We are trying to generate a PET with novel morphologies and unique properties that will be easy to process with retention of all desirable and improved qualities. The initial motivation for this research was the improvement in the properties of PET observed by processing the polymer with cyclodextrins (CDs) 3–5. We have previously observed6 that when polymers are made to form inclusion compounds (ICs) with CDs, and are then coalesced by removing the CD hosts, the resulting CD‐processed polymers are found to behave differently than the as‐received polymers, and this is particularly striking for PET (see Figure 1 and 2).…”

Processing and characterization of extruded PET and its r-PET and MWCNT nanocomposite thin films by spin coating

“…PET was structurally modified by a precipitation technique [15,16]. Briefly, 6% by (w/v) of PET was dissolved in TFA and heated to 50 • C with rapid stirring to completely dissolve the polymer.…”