Crystallization Rate Minima of Poly(ethylene brassylate) at Temperatures Transitioning between Quantized Crystal Thicknesses

Abstract

Poly(ethylene tridecanodiate), also known as poly-(ethylene brassylate) (PEB), is a short−long aliphatic polyester obtained from a renewable source. Cooled from the melt by differential scanning calorimetry or by fast scanning calorimetry, PEBs in a range of molar mass between 27000 and 188000 Da display single crystallization exotherms. On heating, PEBs exhibit two major melt-recrystallization events at ∼40 and ∼60 °C prior to their final melting at ∼70 °C. WAXD patterns collected in situ during heating rule out any polymorphic transition, but SAXS patterns collected at the isothermal crystallization temperatures below and above the highest melt-recrystallization event (∼60 °C) indicate a step increase by one repeating unit of the crystal thickness. The overall isothermal crystallization rate displays two minima at the same temperatures where melt-recrystallization was observed on heating. The minima correspond to the transition between 2−3 repeats (T c = 40 °C) and between 3−4 (T c = 60 °C) monomer repeats in the crystal thickness. A minimum also occurs at the same temperature in the isothermal linear growth rates and is accompanied by a minimum in nucleation density. The observed rate minima at the transition between crystals differing by a quantized thickness are equivalent to the behavior of n-alkanes and low-M w PEO fractions and are also explained by the manifestation of self-poisoning. At T c approaching a rate minimum from above, PEB stems with noninteger repeats attach temporarily to the integer lateral growing surface halting productive growth until they detach or expand to complete the layer. Hence, for this type of polyester, it is the length of the stem approaching the growing surface rather than stems with a different conformation that drives self-poisoning.

Development of Biodegradable Polyesters: Study of Variations in Their Morphological and Thermal Properties through Changes in Composition of Alkyl-Substituted (ε-DL) and Non-Substituted (ε-CL, EB, L-LA) Monomers

“…In Series II, B1 exhibited endotherms at 57, 62 and 68.8 °C ( Figure 6 C) that may be related to semicrystalline arrangements. Additionally, the multiplicity in transitions could be associated with differences in the lamellar thickness [ 35 ]. This thermal performance could be supported in the structural features of EB, taking in consideration its 11 methylene units between carboxylic groups, and so, the macromolecules can acquire several arrangements that are function of carboxylic interaction and stability in the backbone conformation Likewise, B2–B4 exhibited endotherms in a wide temperature range, while B3 and B4 developed melt recrystallization events, in which the presence of a branched comonomer ( ε -DL) had an impact on the crystallization decrease due to decoupled intermolecular interactions.…”

Poisoning by Purity: What Stops Stereocomplex Crystallization in Polylactide Racemate?

“…In long monodisperse n -alkanes, these transitions are from extended- to once-folded , or from once- to twice-folded-chain growth . In sharp low-molecular-weight PEO fractions, it is again from extended- to once-folded chains. , In segmented polydisperse polyethylenes with regularly spaced substituents such as Br or acetal groups, the transitions are between lamellar thicknesses corresponding to an integer number of such chain segments. , In all of these cases just above the growth transition temperature, G of the thicker lamella is obstructed by depositions of shorter, nearly stable chain stems with finite but still reasonably long lifetime. These are cases where Lauritzen–Hoffman theory fails, but fine grain theories like that of Sadler or related approaches by the rate equation , or simulations ,, reproduce the kinetics reasonably well, at least qualitatively.…”

Synthesis, Morphology, and Crystallization Kinetics of Polyheptalactone (PHL)

“…Another potentially interesting aspect could be the presence of one more carbon atom than PCL, which could affect the crystallization. For example, in a recently published study, it was reported that PEB (poly-(ethylene brassylate)), a short-long aliphatic polyester (with 13 methylene groups in its repeat unit), exhibits a peculiar crystallization behavior due to a similar self-poisoning effect to that observed previously in long-chain alkanes. − The self-poisoning effect consists in the display of a crystallization rate minima upon decreasing the isothermal crystallization temperature. In the case of long-chain alkanes, extended-chain lamellae form first at high crystallization temperature, then segments with the folded chain conformation attach, upon decreasing T c values, to the growth front, preventing further growth until they detach, and growth can again proceed in the extended form. − The higher ratio of methylene groups versus ester groups in PEB along the aliphatic chain leads to properties that come closer to that of polyethylene (PE), as the polar group is “diluted” along the nonpolar rest of the chain.…”