Microgel Heterogeneous Morphology Reflected in Temperature-Induced Volume Transition and 1H High-Resolution Transverse Relaxation NMR. The Case of Poly(N-vinylcaprolactam) Microgel
Microgel Heterogeneous Morphology Reflected in Temperature-Induced Volume Transition and 1H High-Resolution Transverse Relaxation NMR. The Case of Poly(N-vinylcaprolactam) Microgel
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DOI：
10.1021/ma200103y
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发表时间：
2011-04-12
期刊：
影响因子：
5.5
通讯作者：
Pich, Andrij
中科院分区：
文献类型：
--
作者：
Balaceanu, Andreea;Demco, Dan E.;Pich, Andrij
推广了均聚微凝胶的Flory温度诱导体积转变理论。从H-1横向弛豫核磁共振和Flory状态方程施加的微观和热力学约束中选择最可能的形态参数，以近似均匀形态。质子横向磁化弛豫核磁共振直接证明了PVCL微凝胶粒子的双峰非均相形态的存在。通过对不同交联方式的聚（n -乙烯基己内酰胺）（PVCL）微凝胶在水中的尺寸-温度数据，得到了聚合物在溶胀状态下的体积分数以及核心和电晕的亚链数。采用动态光散射法研究了不同交联剂用量对交联密度的影响。Flory非均相理论和MAR横向弛豫相结合表明，随着交联剂用量的增加，聚合物核和电晕中的亚链数量增加。此外，通过各衰变分量的横向弛豫时间T-2，可以计算出核和电晕的交联密度比。通过尺寸-温度数据和H-1横向弛豫核磁共振对PVCL微凝胶的定量表征表明了所作假设的一致性。在推广Flory理论的微凝胶的异质形态。
The Flory temperature-induced volume transition theory for homopolymer microgels was generalized for the case of bimodal heterogeneous morphology. The most probable morphological parameters were selected from the microscopic and thermodynamic constraints imposed by H-1 transverse relaxation NMR and Flory equation of state in the approximation of a homogeneous morphology. Proton transverse magnetization relaxation NMR proved directly the existence of a bimodal heterogeneous morphology of the PVCL microgel particle. The volume polymer fractions in the deswollen state and the number of subchains for the core and corona were obtained from size-temperature data for a series of differently cross-linked microgels made of poly(N-vinylcaprolactam) (PVCL) in water. The cross-link density effect given by the different amounts of cross-linker used was investigated using dynamic light scattering. From the combination of Flory heterogeneous theory and MAR transverse relaxation, the number of polymer subchains in core and corona was shown to increase with the amount of cross-linker. Moreover, the ratio of the cross-link density in core and corona could be evaluated from the transverse relaxation times T-2 of each decay components. The quantitative characterization of PVCL microgels by size-temperature data and H-1 transverse relaxation NMR shows the consistency of the assumptions made. in the generalization of Flory theory of microgels for heterogeneous morphology.