PREPARATION OF POLYMERS WITH SECONDARY STRUCTURES SPONTANEOUSLY REGULATED BY HYDROGEN BONDING AMONG SIDE CHAINS AND THEIR APPLICATION AS MOLECULAR DEVICES

通过等规聚甲基丙烯酸侧链羧基与芳香胺的酰胺化反应，合成了主链规整性和侧链结构均可调控的聚甲基丙烯酰胺-S。随后研究了侧链酰胺基团之间的氢键和侧链发色团的取向。侧链含有(S)-1-苯乙基的等规聚甲基丙烯酰胺比含(S)-1-(1-萘基)乙基和其他侧链的等规聚甲基丙烯酰胺形成更广泛的分子内氢键，表明前者在稳定全氢键结构方面具有足够的空间效应。分子力学计算表明，具有S构型侧链基团的全同立构聚甲基丙烯酰胺S具有右旋5_2螺旋。发现当聚甲基丙烯酰胺S呈现完全氢键结构…时，侧链之间的激发能量传递效率显著提高更多的ES。当(L)-1-(1-萘基)乙基和其他具有足够空间位阻的基团引入到侧链中时，这些聚合物呈现出侧链二级结构，发色团沿螺旋主链取向。荧光猝灭实验表明，这些定向发色团能有效地传递激发能。由这些聚合物制备的薄膜的圆二色谱表明，存在三种不同发色团取向的侧链结构。分子力学计算表明存在几种稳定或准稳定的侧链结构，其中一种发生在主链和侧链之间发生氢键，这与红外光谱观察到的侧链酰胺基团广泛氢键的情况一致。也有人认为，这种氢键导致主链构象偏离α-螺旋。正试图将各向异性引入到这些薄膜中。如上所述，全同立构的聚(甲基丙烯酰胺)S和聚(L-谷氨酰胺)S作为分子器件的实用性现已确立。通过在侧基中引入芘和二茂铁等生色团，进一步研究了它们的激发、能量输运和电荷输运功能。较少

Poly (methacrylamide) s with regulated primary structures, i.e., main-chain tacticity and side-chain structure, were prepared by amidation of the side-chain carboxyl groups of isotactic poly (methacrylic acid) with aromatic amines. Hydrogen bonding among the side-chain amide groups and side-chain chromophore orientation were subsequently examined. Isotactic poly (methacrylamide) having (S) -1-phenylethyl groups in the side chains was found to form intramolecular hydrogen bonding more extensively than those having (S) -1- (1-naphthyl) ethyl and other side-chain groups, showing adequate steric effects in the former in stabilizing the fully-hydrogen-bonded structure. Molecular mechanics calculations suggest that the isotactic poly (methacrylamide) s with side-chain groups of S-configuration assume right-handed 5_2 helices. The efficiency of excitation energy transport among the side chains was found to improve markedly when the poly (methacrylamide) s assume fully-hydrogen-bonded structur … More es. These polymers were found to form lamellar structures in films.Poly (L-glutamine) s were found to assume side-chain secondary structures with chromophores oriented along the helical main chain when (S) -1- (1-naphthyl) ethyl groups and others having adequate steric hindrances are introduced in the side chains. Fluorescence quenching experiments showed that excitation energy is transported efficiently through these oriented chromophores. Circular dichroic spectra of films prepared from these polymers showed that there are three types of side-chain structures with varying chromophore orientation. Molecular mechanics calculations suggest there are several stable or quasi-stable side-chain structures, and in one of them hydrogen bonding occurs between the main chain and the side chain in accord with the IR observation that side-chain amide groups are extensively hydrogen-bonded. It is also suggested that such hydrogen bonds cause deviation of the main-chain conformation from alpha-helix. Introduction of anisotropy to these films are now being attempted.As described above, the usefulness of isotactic poly (methacrylamide) s and poly (L-glutamine) s as molecular devices is now established. Their excitation energy transport and charge transport functions are now being investigated further by introducing such chromophores as pyrene and ferrocene in the side groups. Less