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Polypentadecalactone prepared by lipase catalysis: crystallization kinetics and morphology
Author(s) -
Cai Jiali,
Hsiao Benjamin S,
Gross Richard A
Publication year - 2009
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.2624
Subject(s) - crystallography , crystallization , branching (polymer chemistry) , melting point , enthalpy , materials science , surface energy , kinetics , polymer chemistry , lamellar structure , crystallinity , polyethylene , stereochemistry , chemistry , thermodynamics , physics , composite material , quantum mechanics
BACKGROUND: This work addresses the need to better understand the crystallization kinetics and morphology of poly (ω‐pentadecalactone) (PPDL). This polyester has promising mechanical properties and a unique structure that resembles that of polyethylene. PPDL is a member of the poly(ω‐hydroxy fatty acid) family, which can be derived from biobased feedstocks. RESULTS: PPDL ( M n = 34 000 g mol −1 and dispersity D = M w / M n = 2.7) was synthesized using enzyme catalysis. Equilibrium melting enthalpy and equilibrium melting point were determined using extrapolation techniques, being 227 J g −1 and 101 °C, respectively. In addition, the equilibrium melting point ( $T_{\rm {m}}^{0}$ ) was found to be 109.3 °C by the nonlinear Hoffman‐Weeks plot. For $T_{\rm {m}}^{0} = 101.0 ^{\circ}\hbox{C}$ , the lateral surface free energy (σ), fold surface free energy (σ e ) and fold work ( q ) are 10.4 erg cm −2 , 47.5 erg cm −2 and 2.6 kcal mol −1 , respectively; while for $T_{\rm {m}}^{0} = 109.3 ^{\circ}\hbox{C}$ , they are 25.1 erg cm −2 , 46.6 erg cm −2 and 2.6 kcal mol −1 , respectively. The results indicated the existence of a regime I to regime II transition during crystallization at about 80 °C. Polarized optical microscopy and AFM provided further evidence for the regime I–II transition. In regime I, coarse spherulites were formed through splaying out and occasional branching of lamellae, as well as stacking of lamellae through screw dislocation. In contrast, in regime II, banded spherulites were formed through crystal twisting. CONCLUSION: Morphological changes in PPDL at spherulitic and lamellar levels in regimes I and II were confirmed by differential scanning calorimetry, POM and AFM. Copyright © 2009 Society of Chemical Industry