Design, synthesis, and characterization of linear fluorinated poly(benzyl ether)s: A comparison study with isomeric hyperbranched fluoropolymers
作者:Kenya T. Powell、Chong Cheng、Chakravarthy S. Gudipati、Karen L. Wooley
DOI:10.1039/b511555h
日期:——
A well-defined compositionally-equivalent linear analog to a previously reported hyperbranched fluoropolymer (HBFP) was synthesized and each was subjected to characterization studies as a fundamental investigation of the role of architecture on solution and solid-state properties. Condensation polymerization of 3-[(tert-butyl)dimethylsilyl]oxy}-5-[(2′,3′,4′,5′,6′-pentafluoro)oxy]benzyl alcohol in the presence of an excess of elemental sodium dispersion, followed by removal of the TBDMS protecting group, and finally alkylation with 2,3,4,5,6-pentafluorobenzyl bromide afforded linear fluorinated poly(benzyl ether)s (LFP)s. Molecular weights were typically 7000 to 15000 Da (Mn) with molecular weight distributions of ca. 2, as determined by size exclusion chromatography. Confirmation of the isomeric structures of LFP and HBFP was made by 1H, 19F, and 13C NMR, and IR spectroscopies. Evaluation of the effects of molecular architecture on solution behavior were examined by solubility and 19F NMR diffusion measurements. There was no significant difference in solubility in a wide range of organic solvents. 19F NMR diffusion experiments measured diffusion coefficients of ca. 3 × 10−6 cm2 s−1 and estimated Stokes radii of 15–26 Å, depending upon the solvent, regardless of polymer architecture. Differential scanning calorimetry and thermogravimetric analysis studies revealed similar thermolytic profiles with a glass transition temperature of 53 °C for both systems and thermal stability up to 290 °C. Our studies show that the difference in polymer architecture (linear versus hyperbranched) does not necessarily mandate obvious discrepancies in spectroscopic or solution behavior, although the molecular weights for these polymers were maintained at relatively low values.
合成了一个与先前报道的超支化氟聚合物(HBFP)组成等效的明确定义的线性模拟物,并分别对其进行了表征研究,以作为对溶液和固态性质中结构作用的基本调查。在过量的元素钠分散体存在下,通过3-[(叔丁基)二甲基硅基]氧}-5-[(2',3',4',5',6'-五氟)氧]苄醇的缩聚反应,随后去除TBDMS保护基团,最后与2,3,4,5,6-五氟苄溴进行烷基化,得到了线性氟化聚(苄基醚)(LFP)。分子量通常为7000至15000 Da(Mn),分子量分布约为2,由尺寸排阻色谱法确定。通过1H,19F和13C NMR以及IR光谱学确认了LFP和HBFP的异构结构。通过溶解度和19F NMR扩散测量研究了分子结构对溶液行为的影响。在广泛的有机溶剂中,溶解度没有显著差异。19F NMR扩散实验测得的扩散系数约为3 × 10−6 cm2 s−1,估计的斯托克斯半径为15–26 Å,取决于溶剂,与聚合物结构无关。差示扫描量热法和热重分析研究表明,两者具有相似的热分解轮廓,玻璃化转变温度均为53 °C,热稳定性高达290 °C。我们的研究表明,聚合物结构(线性与超支化)的差异不一定导致光谱或溶液行为上的明显差异,尽管这些聚合物的分子量保持在相对较低的值。