Influence of molecular weight on the crystallization of Polyheptalactone (PHL)

Abstract

[EN] The present work studies the characterization of 4 new homopolymers of polyheptalactone (PHL): PHL 15, PHL 35, PHL 66, and PHL 90; focusing on the influence of the molecular weight. These polymers are interesting because they are biodegradable and very similar to polycaprolactone (PCL), with one additional carbon in the repeating unit.

Two main experimental techniques have been used: Differential Scanning Calorimetry (DSC) and Polarised Light Optical Microscopy (PLOM). With these two techniques non-isothermal and isothermal crystallization experiments have been carried out. On the one hand, PLOM has been used in order to study the morphology of the crystals and the crystallization growth kinetics. On the other hand, with the DSC, the main thermal properties of the new polymers and overall crystallization kinetics have been analyzed. Moreover, Transmission Electron Microscopy (TEM) and Wide-Angle X-ray Scattering (WAXS) techniques have provide additional information about polymer morphology.

The main thermal transitions and crystallization kinetics of the four homopolymers have been determined, applying Avrami and Lauritzen and Hoffman theories. Results conclude that these polymers are stable and semycrystalline. Moreover, molecular weight affects in a different way the measured properties. Lamellar thickness and X-ray diffractograms are not affected by the molecular weight while phase transition temperatures and crystallization rates increase when molecular weight rises.

[EU] Lan hau Poliheptalaktonazko (PHL) 4 homopolimero berrien karakterizazioan oinarritu da: PHL 15, PHL 35, PHL 66 eta PHL 90; pisu molekularraren eragina aztertuz. Polimero hauek interesgarriak dira biodegradagarriak direlako eta Polikaprolaktonaren (PCL) oso antzekoak direlako, karbono atomo bat gehiago izanik unitate errepikakorrean.

Nagusiki bi teknika esperimental erabili dira: Ekorketazko Kalorimetria Diferentziala (DSC) eta Argi Polarizatutako Mikroskopio Optikoa (PLOM). Bi teknika hauekin kristalizazio ez-isotermiko eta isotermikoak burutu dira. Alde batetik, PLOM-ren bidez kristalen morfologia eta kristalizazio hazkuntzaren zinetika aztertu da. Bestalde, DSC-ren bidez polimeroaren propietate termiko nagusiak eta kristalizazio osoaren zinetika aztertu dira. Gainera, Transmisio Mikroskopio Elektronikoa (TEM) eta Angelu Zabaleko X-izpi Sakabanaketa (WAXS) teknikek polimeroaren morfologiari buruzko informazio gehigarria eman dute.

4 homopolimeroen trantzisio termikoak eta kristalizazio zinetika determinatu dira, Avrami eta Lauritzen and Hoffman teoriak erabiliz. Emaitzak aztertuz, polimeroak egonkorrak eta semikristalinoak direla ondorioztatu da. Honetaz gain, pisu molekularrak modu desberdinean eragiten du neurtutako propietate eta parametroetan. Lamela lodiera eta X-izpien difraktogramak ez dira aldatzen pisu molekularraren arabera. Fase trantzisio tenperaturak eta kristalizazio abiadurak aldiz pisu molekularrarekin batera handitzen dira.