Secondary Structure and Side-Chain Chromophore Orientation of Isotactic Poly(methacrylamide)s in Solid Film

Abstract

Intramolecular hydrogen bonding among the side-chain amide groups in isotactic poly[(S)-1-(1-naphthyl)ethyl methacrylamide] (1) and poly[(S)-1-phenylethyl methacrylamide] (2) were examined in films cast from I ,2-dichloroethane (EDC). Curve fitting of the amide I band shows that the peaks for the full hydrogen bonds are broader as compared with those in EDC solution, suggesting that the hydrogen bonds formed in film are looser and less extensive than those in solution. X-Ray diffraction (XRD) measurements show that these polymers give hexagonal-like aggregates in film, indicating that they form rod-like helical structures as suggested by molecular mechanics calculations. Isotactic 2 film shows a positive circular dichroic (CD) peak at ca. 230 nm, characteristic of the fully hydrogen-bonded helical structure, which disappears upon annealing. Isotactic 1 film shows two CD positive peaks at ca. 210 nm and at ca. 230 nm, their relative intensities changing upon annealing, which together with the CD measurements in solution suggests that the hydrogen-bonded and non-hydrogen bonded structures of isotactic 1 give, in the 1 Bb band of the naphthyl group, exciton coupling of positive chirality and that of negative chirality, respectively, the overall CD being determined by their relative contents.

Supramolecular Helix–Helix Block Copolymers

“…This agrees well with previously reported X-ray diffraction data of a film prepared from isotactic poly((−)-NEMAM) (DP ≈ 700) which displayed a relatively weak maximum around 12.6 Å. 60,71 Supramolecular Assembly with Small Molecule Analogues. To investigate the supramolecular interaction at the polymer chain-end for HW-Poly and Ba-Poly, small molecule analogues of the complementary recognition units were synthesized according to previously published procedures: tert-butyldimethylsiloxy (TBS) protected Hamilton wedge (sHW) and 5-ethyl-5-(hex-5-yn-1-yl)pyrimidine-2,4,6-(1H,3H,5H)-trione (sBa) (Figures S26 and S29).…”

“…66 Ba-Poly experiences electronic transitions associated with absorbance at 283 and 236 nm for naphthyl π−π* transitions due to intramolecular hydrogen bonding. 60 For both polymer systems, the helical sense of the polymers is dependent on the chiral side-chains. When (−)-menthoxycarbonylphenyl isocyanide is polymerized, a strong positive Cotton effect is observed at 364 nm and is indicative of an excess P-helical sense (HW-Poly-2, Figure 2) as determined by experimental and computational methods.…”

“…Poly­( N -(1-(naphthalen-2-yl)­ethyl)­methacrylamide) (poly­(NEMAM)­s) have been shown to adopt a helical structure based on the chirality of the naphthyl­ethyl side chains. − The secondary helical structure of this polymer is different in comparison to poly­(isocyanide)­s as it features dynamic hydrogen-bonding events along the polymer backbone that affect the overall secondary structure. A commercially available RAFT CTA was modified to contain a terminal barbiturate (Ba), the complementary unit to the HW receptor.…”

Supramolecular Diblock Copolymers Featuring Well‐defined Telechelic Building Blocks

“…[17] Whereas PPV blocks are structurally well-defined and maintain ac rystalline framework, both helical building blocks are less crystalline.B a-PMAc exhibits one weakly intense and broad peak centered at 2q = 7.03, corresponding to an interplanar distance of 12.6 ,a sp reviously reported. [18] Af ew peaks are noted in HW-PIC,the strongest of which corresponds to the diameter of the polymer stem (d = 19.8 ).…”

Supramolecular Diblock Copolymers Featuring Well‐defined Telechelic Building Blocks

“…Other features,c onsistent with dioctyloxy-PPV (DO-PPV), are attributed to the lamellar structure and interbackbone spacing of aligned PPV backbones. [18] Af ew peaks are noted in HW-PIC,the strongest of which corresponds to the diameter of the polymer stem (d = 19.8 ). [18] Af ew peaks are noted in HW-PIC,the strongest of which corresponds to the diameter of the polymer stem (d = 19.8 ).…”