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synthesis, characterization, and enzymatic degradation of poly((r,s)-beta-hydroxybutyrate) of varied tacticities (beta-hydroxybutyrate, racemic, syndiotactic). [microform]
synthesis, characterization, and enzymatic degradation of poly((r,s)-beta-hydroxybutyrate) of varied tacticities (beta-hydroxybutyrate, racemic, syndiotactic). [microform]
상세정보
- 자료유형
- 마이크로피시
- 청구기호
- 저자명
- 서명/저자
- synthesis, characterization, and enzymatic degradation of poly((r,s)-beta-hydroxybutyrate) of varied tacticities (beta-hydroxybutyrate, racemic, syndiotactic). - [microform]
- 발행사항
- 형태사항
- 301 p. : microfiches ; 11×15 cm.
- 총서명
- UMI Dissertation
- 주기사항
- Source: Dissertation Abstracts International, Volume: 57-10, Section: B, page: 6285.
- 학위논문주기
- thesis (ph.d.)-- - mcgill university (canada), 1996.
- 초록/해제
- 요약Poly ((R)-$\beta$-hydroxybutyrate), PHB, is a naturally-occurring thermoplastic polyester of widespread interest due to its inherent biodegradability. A synthetic racemic analogue, poly ((R,S)-$\beta$-hydroxybutyrate), was prepared via the methylaluminoxane-catalyzed polymerization of (R,S)-$\beta$-butyrolactone, and fractionated to yield a range of tacticities, including new material primarily syndiotactic in nature. Each fraction was characterized, and the syndiotactic crystal structure was examined. An x-ray fibre diagram was recorded, the measured reflections were indexed, and a tetragonal unit cell was assigned.
- 초록/해제
- 요약To supplement the initial characterization and probe the polymerization mechanism, high resolution $\sp{13}$C nmr spectra were obtained for the full tacticity range of the racemic PHB and interpreted with regard to several statistical models. A two-site model involving enantiomorphic and first-order Markovian sites was proposed, and the parameters describing each sample were derived. Average isotactic and syndiotactic block lengths were also calculated.
- 초록/해제
- 요약The connection between stereoregularity and crystalline morphology was probed through the precipitation of single crystals. Lamellar single crystals similar to those of bacterial PHB were obtained from isotactic racemic PHB even of low stereoregularity; syndiotactic PHB gave a non-diffracting precipitate of two morphologies apparently differing in tacticity. Cocrystallization of R and S repeat units was implied.
- 초록/해제
- 요약In recognition of the important of biodegradation to the interest in this material, the enzymatic degradability of the synthetic PHB was investigated, using extracellular PHB depolymerases of both bacterial and fungal origin. For solvent-cast films of PHB, the rates of weight loss decreased in the order bacterial PHB $$ synthetic atactic $$ synthetic isotactic $$ synthetic syndiotactic in both enzyme systems. The relative degradation rates of the synthetic samples changed significantly when the single crystals of natural and synthetic PHB were degraded. These observations were interpreted in terms of the opposing effects of crystallinity and stereochemistry, and the assumed normalization of crystallinity differenced in the single crystals of different tacticity. Differenced between the two enzyme systems, preferential enzymatic attack on the edge or fold surfaces of the single crystals, and the implications in terms of chain cleavage mechanism were also examined.
- 복제주기
- Microfiche : UMI . microfiches;11×15 cm.
- 일반주제명
- 일반주제명
- 일반주제명
- 키워드
- 기타저자
- 기본자료저록
- Dissertation Abstracts International. 57-10B.
MARC
008970923s1996 us eng■001MOKWON00234116
■001AAVNN12383
■00519990922110620
■008970923s1996 us eng
■020 ▼a0612123839
■035 ▼a(UnM)AAVNN12383
■040 ▼aUnM▼cUnM▼dMOKWON
■090 ▼a540▼bH685s
■1001 ▼ahocking, philippa jane.
■24510▼asynthesis, characterization, and enzymatic degradation of poly((r,s)-beta-hydroxybutyrate) of varied tacticities (beta-hydroxybutyrate, racemic, syndiotactic).▼h[microform]
■260 ▼aU.S.▼bmcgill university (canada)▼c1996.
■300 ▼a301 p.▼bmicrofiches▼c11×15 cm.
■350 ▼a$50.6
■44000▼aUMI Dissertation
■500 ▼aSource: Dissertation Abstracts International, Volume: 57-10, Section: B, page: 6285.
■502 ▼athesis (ph.d.)--▼bmcgill university (canada)▼d1996.
■520 ▼aPoly ((R)-$\beta$-hydroxybutyrate), PHB, is a naturally-occurring thermoplastic polyester of widespread interest due to its inherent biodegradability. A synthetic racemic analogue, poly ((R,S)-$\beta$-hydroxybutyrate), was prepared via the methylaluminoxane-catalyzed polymerization of (R,S)-$\beta$-butyrolactone, and fractionated to yield a range of tacticities, including new material primarily syndiotactic in nature. Each fraction was characterized, and the syndiotactic crystal structure was examined. An x-ray fibre diagram was recorded, the measured reflections were indexed, and a tetragonal unit cell was assigned.
■520 ▼aTo supplement the initial characterization and probe the polymerization mechanism, high resolution $\sp{13}$C nmr spectra were obtained for the full tacticity range of the racemic PHB and interpreted with regard to several statistical models. A two-site model involving enantiomorphic and first-order Markovian sites was proposed, and the parameters describing each sample were derived. Average isotactic and syndiotactic block lengths were also calculated.
■520 ▼aThe connection between stereoregularity and crystalline morphology was probed through the precipitation of single crystals. Lamellar single crystals similar to those of bacterial PHB were obtained from isotactic racemic PHB even of low stereoregularity; syndiotactic PHB gave a non-diffracting precipitate of two morphologies apparently differing in tacticity. Cocrystallization of R and S repeat units was implied.
■520 ▼aIn recognition of the important of biodegradation to the interest in this material, the enzymatic degradability of the synthetic PHB was investigated, using extracellular PHB depolymerases of both bacterial and fungal origin. For solvent-cast films of PHB, the rates of weight loss decreased in the order bacterial PHB $$ synthetic atactic $$ synthetic isotactic $$ synthetic syndiotactic in both enzyme systems. The relative degradation rates of the synthetic samples changed significantly when the single crystals of natural and synthetic PHB were degraded. These observations were interpreted in terms of the opposing effects of crystallinity and stereochemistry, and the assumed normalization of crystallinity differenced in the single crystals of different tacticity. Differenced between the two enzyme systems, preferential enzymatic attack on the edge or fold surfaces of the single crystals, and the implications in terms of chain cleavage mechanism were also examined.
■533 ▼aMicrofiche▼cUMI▼emicrofiches;11×15 cm.
■590 ▼aSchool code: 0781.
■650 4▼aChemistry, Polymer
■650 4▼aEngineering, Materials Science
■650 4▼aPlastics Technology
■653 ▼asynthesis▼acharacterization▼aand▼aenzymatic▼adegradation▼aof▼apoly((r,s)-beta-hydroxybutyrate)▼aof▼avaried▼atacticities▼a▼a(beta-hydroxybutyrate▼aracemic▼asyndiotactic).
■690 ▼a0495
■690 ▼a0794
■690 ▼a0795
■71020▼amcgill university (canada).
■7730 ▼tDissertation Abstracts International▼g57-10B.
■790 ▼a0781
■791 ▼aPH.D.
■792 ▼a1996
