Effects of Steric Repulsion on Helical Conformation of Poly(N-propargylamides) with Phenyl Groups

Abstract

N-Propargylamides with one, two, and three phenyl groups at the R-position of the carboxyl group [HC≡CCH2NHCOR; 1, R ) C(CH3)2C6H5; 2, R ) CCH3(C6H5)2; 3, R ) C(C6H5)3] were polymerized with a rhodium catalyst, (nbd)Rh + B -(C6H5)4 (nbd ) 2,5-norbornadiene), to obtain the corresponding polymers in 85-91% yields. Poly(1) possessed a moderate molecular weight (Mn ) 6300) and was thoroughly soluble in chloroform and dichloromethane. On the other hand, poly(2) and poly(3) were not totally soluble in the solvents. The Mn's of chloroform-soluble parts were less than 3000. The secondary structure of these three polymers in chloroform was examined by UV-vis spectroscopy with varying temperature. It was found that only poly(1) could adopt helical conformation even at 60 °C. By the copolymerization of either monomer 2 or 3 with HC≡CNH2CO(CH2)4H ( 4), the solubility of the polymers was effectively improved, and the Mn's were remarkably increased. When the content of unit 4 in poly-(2-co-4)s was 25% and above, the copolymers could form helical conformation with different degrees, among which poly(20.40-co-40.60) showed the largest helicity. When the content of unit 4 of poly(3-co-4)s exceeded 95%, the copolymer took helical structure partly.

A Novel Type of Mono-Substituted Polyacetylene: Synthesis and Characterization of Poly(N-Propargylthiourea)s

“…In the spectrum of M4, only one strong absorption peak could be observed at around 265 nm, originating in the thiourea and phenyl ring in the monomer [32]. In the spectrum of poly(4), besides the absorption peak around 265 nm, we can see a moderate absorption at about 310 nm, supporting the fact that poly(4) possess conjugated polyacetylene backbones [33]. The results with respect to UV-Vis absorption spectra are similar to some mono-substituted polyacetylenes studied by us earlier, e.g., poly(N -propargylsulfamide)s [34] and poly(N -propargylurea)s [26].…”

Polymerization of Substituted Acetylenes by the Grubbs–Hoveyda Ru Carbene Complex

“…Rh catalysts can polymerize only monosubstituted acetylenes such as phenylacetylene and its ring-substituted derivatives, [6][7][8][9][10][11] N-propargylamides, [12][13][14][15][16][17] and propiolic esters. [19][20][21][22][23] The Rh-catalyzed polymerization proceeds by the insertion mechanism, and features excellent tolerance to polar subsituents in the monomer 24,25 and protic solvents.…”

Synthesis and Properties of Helical Poly(macromonomer) Consisting of Polyacetylene Main Chain and Poly(methyl methacrylate) Side Chains

“…[24][25][26][27][28][29] However, the cis olefinic proton signal was not observed in the 1 H NMR spectrum of poly(M-PMMA), probably because of the low mobility of the polyacetylene main chain. 50 The GPC traces of M-PMMA and poly(M-PMMA) (Run 4, Table I) are illustrated in Figure 2.…”

“…[1][2][3][4][5] There are several classes of wellordered synthetic helical polymers including poly-(alkyl methacrylates), [6][7][8][9] polychloral, 10,11 polyisocyanides, [12][13][14][15] polyisocyanates, [16][17][18][19] and polysilanes. [20][21][22][23] Besides, some helical polyacetylenes have been synthesized by Rh-catalyzed polymerization of acetylenic monomers having chiral side groups such as chiral carboxylic acids, [24][25][26][27][28][29] alcohols, [30][31][32][33] amino acids, [34][35][36][37][38][39][40] sugars [41][42][43] and terpenes 44 as the helical sources. Recently, our laboratory reported that (S)-1-methylpropargyl alcohol served as a powerful helical source for substituted polyacetylenes.…”