Sequences distribution of poly(ethylene terephthalate‐isophthalate) copolymers: Experimental TREF study and numerical simulation

Abstract

The fractionation of a statistical copolyester made of poly(ethy1ene terephthalate-isophthalate) has been performed using Temperature Rising Elution Fractionation (TREF). TREF fractions were analyzed by size exclusion chromatography, thermal analysis, 'H-nuclear magnetic resonance and small angle X-Ray diffractometry. Results show that the fractions exhibit both interchain and intrachain defect distribution. As the intrachain defect distribution can not be determined by experimental techniques, a computer simulation based on the determination of terephthalic sequences length in a virtual polymeric distribution was performed. The simulated chains were constructed using a stochastic process. The analysis of the results obtained on the distribution of the simulated sequences in the polymer correlates quantitatively well between the new fractionation mechanism proposed for copolyesters and the experimental results.

Tacticity distribution of isotactic polypropylene prepared with heterogeneous Ziegler–Natta catalyst. 2. Application and analysis of SSA data for polypropylene

“…A collection of chains with similar longest crystallisable sequences can still contain a broad intra-molecular distribution of crystallisable sequence lengths, which explains the presence of multiple melting peaks. In an analogous case, Lodefier et al [28,29] have shown that the TREF fractions of random copolyester have broad stepwise isothermal segregation technique melting curves, because of the broad intra-molecular distribution of crystallisable sequence lengths in the chains. The narrower peaks of the highermelting fractions indicate that these fractions contain more uniform material.…”

Poly(ethylene terephthalate) copolymers that contain 5‐tert‐butylisophthalic acid and 1‐3/1‐4‐cyclohexanedimethanol: Synthesis, characterization, and properties

“…The incorporation of the isophthalic units into PET causes a steady decrease in the T g of PET. [9][10][11][12][13][14][15] This trend is reversed, however, when the isophthalic units are replaced by t BI units. [16][17][18][19] The variation of the T g with the content of t BI unit along the five series (CHDM contents ¼ 0, 5, 10, 15, and 20%) is compared in Table I, revealing that a nearly linear trend is followed in every case.…”

“…[9][10][11][12][13][14][15] Table I shows how T g varies as the content of CHDM increases (PET, PETG 5 , PETG 10 , PETG 15 , and PETG 20 ).…”

“…Due to its good commercial accessibility, the utilization of isophthalic acid as the second acidic comonomer has been extensively investigated to reduce the tendency of PET to crystallize. [9][10][11][12][13][14][15] However, PET copolymers containing isophthalic acid have a glass-transition temperature (T g ) that is lower than that of PET, which constitutes a serious shortcoming of these copolyesters. The utilization of isophthalic acid with bulky side groups that enhance chain stiffness is considered to be a valuable alternative.…”

Poly(ethylene terephthalate) copolymers containing 5‐tert‐butyl isophthalic units

“…PET copolymers containing minor amounts of isophthalic acid as the second comonomer have been extensively investigated for their great industrial importance 5–10. In these copolymers, the sterical disturbance created by the 1,3‐phenylene units in the chain of PET is known to repress considerably the crystallization rate and to restrict the occurrence of crystallinity to compositions in isophthalic acid lower than 20 mol % 6, 7.…”