Polymorphic packing and dynamics of biodegradable poly(3-hydroxypropionate).
Polymorphic packing and dynamics of biodegradable poly(3-hydroxypropionate).
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DOI：
10.1021/jp801538p
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发表时间：
2008-07
期刊：
影响因子：
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通讯作者：
Bo Zhu;Weihua Kai;Pengju Pan;Koji Yazawa;H. Nishida;M. Sakurai;Y. Inoue
中科院分区：
文献类型：
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作者：
Bo Zhu;Weihua Kai;Pengju Pan;Koji Yazawa;H. Nishida;M. Sakurai;Y. Inoue
利用变温红外光谱（FTIR）和固体核磁共振（13 C SNMR）研究了细菌聚3-羟基烷酸酯（P3 HP）的基本骨架--β、γ和δ-聚3-羟基丙酸酯（P3 HP）的堆积和动力学.在冷却条件下，1500-750 cm（-1）范围内的大部分红外吸收带发生明显的蓝移和增强，这反映了分子间相互作用的增强，并取决于每种晶型的链堆积。此外，发现γ型在CH_2弯曲和摇摆处，δ型在CH_2弯曲和C-O-C伸缩处，而β型在CH_2弯曲和C-O-C伸缩处没有温度依赖的振动劈裂。所有的FTIR结果表明，γ-型比β-型具有更强的分子间相互作用，尽管两者都采用全反式构象。在加热过程中测量的IR证据进一步揭示，紧密堆积的γ-形式的熔融将通过一些中间相，其缺乏规则堆积，但保持沿着链的长程有序。δ-型也被发现是紧密堆积的，并且在一个晶胞中至少和最可能包含两个链。比较了δ型、β型和γ型的CP/MAS（13）C SNMR谱，并结合γ-Gauche效应和γ-遮蔽效应对δ型的CP/MAS（13）C SNMR谱进行了解释。考虑到三种晶型之间磁偶极-偶极相互作用的可能差异，通过（13）C自旋-晶格弛豫时间的值来估计晶相的分子迁移率，排序为δ <<γ <<β。从P3 HP的堆积和构象两个方面讨论了P3 HP的三种晶型的不同迁移率，这是P3 HP的晶体结构依赖性生物降解性的关键。
The packing and dynamics of the beta-, gamma-, and delta-forms of poly(3-hydroxypropionate) (P3HP), which represents the basic skeleton of bacterial poly(3-hydroxyalkanoate)s, were investigated by the variable-temperature FTIR and (13)C solid-state NMR measurements (SNMR). Under cooling, most of IR bands in the 1500-750 cm(-1) region were noted to be distinctively blueshifted and enhanced, which should reflect the increased intermolecular interaction and depend on the chain packing of each crystal form. Furthermore, the temperature-dependent splitting of vibration were found to occur at the CH2 bending and rocking for the gamma-form, and at the CH2 bending and C-O-C stretching for the delta-form, while be absent for the beta-form. All the FTIR results indicate that the gamma-form has a stronger intermolecular interaction than the beta-form, although both adopt the all-trans conformation. The IR evidence measured during heating further reveal that the melting of the tightly packed gamma-form would pass through some mesophase, which lacks the regular packing but hold the long-range order along the chains. The delta-form was also found to be tightly packed, and contain at least and most possibly two chains in one unit cell. The CP/MAS (13)C SNMR spectrum of the delta-form was compared with those of the beta- and gamma-forms, and was well explained by combining the gamma-gauche and gamma-eclipsed effects. With considering possible differences in the magnetic dipole-dipole interaction among three crystal forms, the molecular mobilities of crystalline phases were estimated by the values of (13)C spin-lattice relaxation time to rank as delta << gamma << beta. The diversified mobilities of three polymorphic crystalline phases, which is the key to crystalline-structure dependent biodegradability of P3HP, were discussed with considering the packing and conformation.