NMR diffusion and relaxation studies of the encapsulation of fragrances by amphiphilic multiarm star block copolymers
NMR diffusion and relaxation studies of the encapsulation of fragrances by amphiphilic multiarm star block copolymers
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DOI：
10.1021/ma070222i
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发表时间：
2007-07-24
期刊：
影响因子：
5.5
通讯作者：
Sommer, Horst
中科院分区：
文献类型：
--
作者：
Fieber, Wolfgang;Herrmann, Andreas;Sommer, Horst
自扩散核磁共振谱和弛豫法已被用来研究香料包封在水溶性，两亲性星星嵌段共聚物。四种不同的香料分子的自由形式和在聚合物的存在下的扩散系数已被确定，并用于计算的有效程度的封装。在稀水溶液中，65%至99%的客体分子被捕获在聚合物内。包封的程度取决于客体分子的疏水性，由辛醇/水分配系数（log P-OW）表示，其中高log P-OW分子几乎定量地溶解在聚合物中。芳香分子主要位于聚合物的疏水核中，其紧密堆积，而亲水壳是柔性的，仅占一小部分。质子纵向（T-1）和横向（T-2）的香料分子的弛豫时间显着减少的聚合物的存在下，表明较慢的旋转相关时间，由于在疏水性核心的微溶解。
Self-diffusion NMR spectroscopy and relaxometry have been employed to study fragrance encapsulation in water-soluble, amphiphilic star block copolymers. Diffusion coefficients of four different fragrance molecules in the free form and in the presence of the polymer have been determined and used to calculate the effective degree of encapsulation. In dilute aqueous solutions between 65% and 99% of the guest molecules are trapped inside the polymer. The degree of encapsulation depends on the hydrophobicity of the guest molecule, expressed by the octanol/water partitioning coefficient (log P-OW), where high log P-OW molecules are nearly quantitatively dissolved in the polymer. The fragrance molecules are mainly located in the hydrophobic core of the polymer, which is tightly packed, whereas the hydrophilic shell is flexible and takes up only a small percentage. Proton longitudinal (T-1) and transverse (T-2) relaxation times of the fragrance molecules are significantly reduced in the presence of the polymer indicating slower rotational correlation times due to microsolubilization in the hydrophobic core.