Premium
Cyanophenoxy‐containing microbial polyesters: Structural analysis, thermal properties, second harmonic generation and in‐vivo biodegradability
Author(s) -
Gross Richard A.,
Kim Ohyoung,
Rutherford Denise R.,
Newmark Richard A.
Publication year - 1996
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/(sici)1097-0126(199603)39:3<205::aid-pi495>3.0.co;2-9
Subject(s) - heteronuclear molecule , polyester , differential scanning calorimetry , materials science , biodegradation , heteronuclear single quantum coherence spectroscopy , analytical chemistry (journal) , crystallography , chemistry , organic chemistry , molecule , nuclear magnetic resonance spectroscopy , physics , thermodynamics
Pseudomonas putida KT 2442 was utilized as biocatalyst to form optoactive poly(β‐hydroxyalkanoate)s (PHAs) from a cosubstrate mixture of octanoate and the achiral polarizable carbon source 6(4‐cyanophenoxy)hexanoate, CPH. COSY and heteronuclear multiplet quantum correlation experiments were used to assign 1 H and 13 C NMR signals of 3‐hydroxy‐6(4‐cyanophenoxy)hexanoate (3HCPH) repeat units. The methine carbon of 3HCPH repeat units was sensitive to repeat unit sequence effects, indicating that a substantial fraction of 3HCPH centered triad sequences in the product contain neighboring 3‐hydroxyoctanoate and 3‐hydroxhexanoate repeat units. Comparing the thermal properties of 0 and 19.6 mol% 3HCPH samples by differential scanning calorimetry shows that 3HCPH incorporation results in melting at temperatures >64°C (not seen for the 0 mol% sample), more rapid crystallization and a new T g transition at ∼ −21°C. These characteristics indicate that chains and/or chain segments are formed that are enriched in 3HCPH which phaseseparate and form a unique crystal structure. Measurements of second harmonic generation (SHG) intensities carried out using in‐situ corona‐poled samples showed weak SHG signals that increased by a factor of 8 for an increase in the 3HCPH content from 26 to 34 mol%. Comparatively higher SHG intensities (5 times) were found for PHAs which contained 5.1 mol% 3‐hydroxy‐6(4‐nitrophenoxy)hexanoate (3HNPH) repeat units relative to a PHA with 17 mol% 3HCPH. In‐vivo biodegradation studies of microbial polyesters prepared with and without 3HCPH repeat units showed that PHA chains with 3HCPH degraded to lesser extents (weight loss of ∼ 20 and 50% over 72 h incubations). The large increase in polydispersity from 1.9 to 4.3 observed during in‐vivo biodegradation of microbial polyesters containing 3HCPH repeat units was attributed to the existence of chains with highly variable contents of 3HCPH repeat units.