Abstract
Predominantly syndiotactic poly(β-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemic β-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often ∼ 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T c ) of 30°C. At T c values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent on T c and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at ∼ 50°C. This result showed little to no dependence on syn-PHB syndio-regularity and T c . Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between ∼ 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition on T c it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M n =83,700 g/mol) and a 0.64-syn-PHB (M n =11,900 g/mol) were ∼ 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.
| Language | English |
|---|---|
| Pages | 37-47 |
| Number of pages | 11 |
| Journal | Journal of Environmental Polymer Degradation |
| Volume | 3 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Jan 1995 |
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Keywords
- crystallization
- Poly(3-hydroxybutyrate)
- ring-opening polymerization
- syndioregularity
- syndiotactic
- thermal properties
- X-ray diffraction
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Crystallization behavior of predominantly syndiotactic poly(β-hydroxybutyrate). / Kemnitzer, John E.; Gross, Richard A.; McCarthy, Stephen P.; Liggat, John; Blundell, David J.; Cox, Mike.
In: Journal of Environmental Polymer Degradation, Vol. 3, No. 1, 01.01.1995, p. 37-47.Research output: Contribution to journal › Article
TY - JOUR
T1 - Crystallization behavior of predominantly syndiotactic poly(β-hydroxybutyrate)
AU - Kemnitzer, John E.
AU - Gross, Richard A.
AU - McCarthy, Stephen P.
AU - Liggat, John
AU - Blundell, David J.
AU - Cox, Mike
PY - 1995/1/1
Y1 - 1995/1/1
N2 - Predominantly syndiotactic poly(β-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemic β-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often ∼ 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T c ) of 30°C. At T c values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent on T c and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at ∼ 50°C. This result showed little to no dependence on syn-PHB syndio-regularity and T c . Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between ∼ 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition on T c it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M n =83,700 g/mol) and a 0.64-syn-PHB (M n =11,900 g/mol) were ∼ 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.
AB - Predominantly syndiotactic poly(β-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemic β-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often ∼ 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T c ) of 30°C. At T c values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent on T c and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at ∼ 50°C. This result showed little to no dependence on syn-PHB syndio-regularity and T c . Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between ∼ 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition on T c it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M n =83,700 g/mol) and a 0.64-syn-PHB (M n =11,900 g/mol) were ∼ 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.
KW - crystallization
KW - Poly(3-hydroxybutyrate)
KW - ring-opening polymerization
KW - syndioregularity
KW - syndiotactic
KW - thermal properties
KW - X-ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=33744900125&partnerID=8YFLogxK
U2 - 10.1007/BF02067792
DO - 10.1007/BF02067792
M3 - Article
VL - 3
SP - 37
EP - 47
JO - Journal of Polymers and the Environment
T2 - Journal of Polymers and the Environment
JF - Journal of Polymers and the Environment
SN - 1566-2543
IS - 1
ER -