Synthesis and Properties of Polyimides Containing Multiple Alkyl Side Chains

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• 作者：David H. Wang ; Zhihao Shen ; Mingming Guo ; Stephen Z. D. Cheng ; Frank W. Harris
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：February 20, 2007
• 年：2007
• 卷：40
• 期：4
• 页码：889 - 900
• 全文大小：470K
• 年卷期：v.40,no.4(February 20, 2007)
• ISSN：1520-5835

文摘

A series of diamine monomers, i.e., 2,2'-bis{4-[3,4,5-tris(n-alkan-1-yloxy)benzoate]}-4,4'-biphenyldiamines containing multiple alkyl side chains, were synthesized in which the length of the alkyl side chainswas varied from 5 to 18 carbon atoms. Polyimides were prepared from the diamines and pyromellitic dianhydride(PMDA), 3,3'4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2'-dibromo-4,4',5,5'-biphenyltetracarboxylicdianhydride (DBBPDA), and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), respectively,using a one-step method in 1,2-dichlorobenzene or 1-chloronaphthalene. Most of the polymers had good solubilityin chlorinated solvents. Several copolyimides were prepared: BPDA, 2,2'-bis(trifluoromethyl)benzidine (PFMB),and C14 and C16 diamines. The solubility of copolyimides was dramatically affected by different monomeraddition sequences. The high-molecular-weight polyimides could be solution cast into flexible, tough films exceptfor those based on PMDA. The side chains that contained at least 10 carbon atoms crystallized. The meltingpoints of the crystalline regions increased as the length of the side chains increased. Variable-temperature (VT)solid state ¹³C nuclear magnetic resonance (NMR) showed that the polyimide containing C18 side chains crystallizedat room temperature. A wide-angle X-ray diffraction (WAXD) study showed that the spacing between the mainchains increased as the number of carbon atoms in the side chains increased. The diameter of aggregated backboneswas 2.14 nm, indicating several polyimide main chains stacked each other to form supermolecular, nanoscalestructures. Three polyimides and one copolyimide were used to prepare alignment layers. The films generatedliquid crystal pretilt angles of 6, 9, 90, and 90f">, respectively.