Phani Kumar Bandaru V N, Stapf Siegfried, Mattea Carlos
Department of Technical Physics II/Polymer Physics, Institute of Physics , Ilmenau University of Technology , Ilmenau , Germany.
Langmuir. 2019 Jan 15;35(2):435-445. doi: 10.1021/acs.langmuir.8b03057. Epub 2019 Jan 4.
Associative block copolymers of the type (EO) (PO) (EO) (where EO and PO represent ethylene and propylene oxides, respectively) in aqueous solution have far reaching commercial applications such as solubilization, controlled-drug delivery, etc. The molecular dynamics of a self-associating triblock copolymer (EO)(PO)(EO) (known as P123 with a molecular weight of ∼5800), in aqueous solution (DO), consisting of various lyotropic liquid crystalline phases such as isotropic micellar, cubic, hexagonal, and lamellar phases, is investigated using the fast field cycling nuclear magnetic resonance (FFC NMR) relaxometry technique in the Larmor frequency range from 5 kHz to 30 MHz. A nuclear spin-relaxation model consisting of chain modes (Rouse modes) and order fluctuation (OF) modes typical for polymers and liquid crystals, respectively, is considered to explain the observed proton magnetic relaxation dispersion (PMRD) data in the lyophases under investigation. The PMRD analysis in both isotropic micellar and cubic phases revealed a Rouse frequency dependence of spin-lattice relaxation rate ( R), i.e., R ∝ -τ ln(ωτ), in the entire frequency range of study. Hexagonal and lamellar phase data show Rouse modes as well as OF modes, leaving the signature of the latter as R ∝ ω, where p ∼ 0.5 is typical for nematic mesogens. The activation energies were also determined from segmental correlation times in the lyophases of study. To the best of our knowledge, the present FFC NMR relaxometry study is unique and quantitative in unraveling molecular dynamics of the associative copolymer P123 in aqueous solution.
（环氧乙烷）（环氧丙烷）（环氧乙烷）类型的缔合嵌段共聚物（其中环氧乙烷和环氧丙烷分别代表乙烯氧化物和丙烯氧化物）在水溶液中具有广泛的商业应用，如增溶、控释给药等。使用快速场循环核磁共振（FFC NMR）弛豫测量技术，在5 kHz至30 MHz的拉莫尔频率范围内，研究了一种自缔合三嵌段共聚物（环氧乙烷）（环氧丙烷）（环氧乙烷）（称为P123，分子量约为5800）在水溶液（DO）中的分子动力学，该水溶液由各向同性胶束、立方、六方和层状相等多种溶致液晶相组成。考虑了一个由聚合物和液晶分别典型的链模式（劳斯模式）和有序涨落（OF）模式组成的核自旋弛豫模型，以解释在所研究的冻干相中观察到的质子磁共振色散（PMRD）数据。在各向同性胶束相和立方相中的PMRD分析表明，在整个研究频率范围内，自旋晶格弛豫率（R）与劳斯频率有关，即R ∝ -τ ln(ωτ)。六方相和层状相数据显示出劳斯模式以及OF模式，后者的特征为R ∝ ω^p，其中p ∼ 0.5是向列型液晶元的典型值。还从所研究冻干相中的链段相关时间确定了活化能。据我们所知，目前的FFC NMR弛豫测量研究在揭示缔合共聚物P123在水溶液中的分子动力学方面是独特且定量的。
