Enthalpy of melting of α′- and α-crystals of poly(l-lactic acid). (September 2015)
- Record Type:
- Journal Article
- Title:
- Enthalpy of melting of α′- and α-crystals of poly(l-lactic acid). (September 2015)
- Main Title:
- Enthalpy of melting of α′- and α-crystals of poly(l-lactic acid)
- Authors:
- Righetti, Maria Cristina
Gazzano, Massimo
Di Lorenzo, Maria Laura
Androsch, René - Abstract:
- Graphical abstract: Highlights: The temperature-dependence of Δ hm ° of α′- and α-crystals of PLLA is determined. α′- and α-crystals of PLLA have different melting enthalpy. At the melting temperature, Δ hm ° of the α′-form is 107 J g −1 . At the melting temperature, Δ hm ° of the α-form is 143 J g −1 . The lower Δ hm ° value of the α′-form is linked to conformational defects. Abstract: Literature values of the enthalpy of melting (Δ hm °) of 100% crystalline poly(l -lactic acid) (PLLA) vary in a wide range (82–203 J g –1 ). In most cases, such values were determined without taking into account the presence of α′- or α-crystal modifications, or the influence of d -lactic acid units in the analyzed poly(lactic acid). The bulk enthalpy of melting was determined for the stable orthorhombic α form in only few studies, and thermodynamic properties of the metastable α′-modification are not available yet. In the present work, the temperature dependence of Δ hm ° for both the α′- and α-crystal polymorphs of PLLA are determined, by combining differential scanning calorimetry and X-ray diffraction. It is proven that the enthalpies of melting of α′- and α-crystals of 100% crystalline PLLA are different. At the respective melting temperatures of 150 °C and 180 °C, the Δ hm ° values of the α′- and α-forms are 107 and 143 J g −1 . At identical temperature, the enthalpy of melting of α′-crystals is approximately 25 J g −1 lower than that of the α-form. This observation is rationalizedGraphical abstract: Highlights: The temperature-dependence of Δ hm ° of α′- and α-crystals of PLLA is determined. α′- and α-crystals of PLLA have different melting enthalpy. At the melting temperature, Δ hm ° of the α′-form is 107 J g −1 . At the melting temperature, Δ hm ° of the α-form is 143 J g −1 . The lower Δ hm ° value of the α′-form is linked to conformational defects. Abstract: Literature values of the enthalpy of melting (Δ hm °) of 100% crystalline poly(l -lactic acid) (PLLA) vary in a wide range (82–203 J g –1 ). In most cases, such values were determined without taking into account the presence of α′- or α-crystal modifications, or the influence of d -lactic acid units in the analyzed poly(lactic acid). The bulk enthalpy of melting was determined for the stable orthorhombic α form in only few studies, and thermodynamic properties of the metastable α′-modification are not available yet. In the present work, the temperature dependence of Δ hm ° for both the α′- and α-crystal polymorphs of PLLA are determined, by combining differential scanning calorimetry and X-ray diffraction. It is proven that the enthalpies of melting of α′- and α-crystals of 100% crystalline PLLA are different. At the respective melting temperatures of 150 °C and 180 °C, the Δ hm ° values of the α′- and α-forms are 107 and 143 J g −1 . At identical temperature, the enthalpy of melting of α′-crystals is approximately 25 J g −1 lower than that of the α-form. This observation is rationalized taking into account the presence of conformational defects in the disordered α′-modification. … (more)
- Is Part Of:
- European polymer journal. Volume 70(2015)
- Journal:
- European polymer journal
- Issue:
- Volume 70(2015)
- Issue Display:
- Volume 70, Issue 2015 (2015)
- Year:
- 2015
- Volume:
- 70
- Issue:
- 2015
- Issue Sort Value:
- 2015-0070-2015-0000
- Page Start:
- 215
- Page End:
- 220
- Publication Date:
- 2015-09
- Subjects:
- Poly(l-lactic acid) -- Enthalpy of melting -- α′- and α-crystals
Polymers -- Periodicals
Polymerization -- Periodicals
Polymères -- Périodiques
Polymérisation -- Périodiques
Polymerization
Polymers
Periodicals
Electronic journals
547.705 - Journal URLs:
- http://www.sciencedirect.com/science/journal/00143057 ↗
http://www.elsevier.com/journals ↗ - DOI:
- 10.1016/j.eurpolymj.2015.07.024 ↗
- Languages:
- English
- ISSNs:
- 0014-3057
- Deposit Type:
- Legaldeposit
- View Content:
- Available online (eLD content is only available in our Reading Rooms) ↗
- Physical Locations:
- British Library DSC - 3829.791000
British Library DSC - BLDSS-3PM
British Library HMNTS - ELD Digital store - Ingest File:
- 20942.xml