Investigation of macromolecules exhibiting the structure of a once-broken rod by molecular optics. 2. Synthesis and investigation of three-block copolymers: poly(γ-benzyl L-glutamate)-poly(methyl methacrylate)-poly(γ-benzyl L-glutamate)

Ul’yanova, N. N.; Baranovskaya, I.A.; Liubina, S. Ya.; Безрукова, М. А.; Rudkovskaya, G.D.; Sabsels, B.; Vlasov, G. P.; Eskin, V. E.

doi:10.1021/ma00011a044

Cited by 6 publications

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“…However, hinged polymers such as PAzP can be heterogeneous in the location of the molecular hinge within the backbone, and contamination by the homopolymer (e.g., PAz) can have an important influence on physical properties such as dipole moment and relaxation. Past studies in which a flexible alkyl‐diamine was used as an initiator to prepare once‐broken polypeptides were hampered in unambiguously demonstrating a hinged structure for the polymers 8, 10. Nakagawa et al24 used measurements of polymerization rate and optical rotation to infer the structure of the once‐broken rod.…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, intramolecular hydrogen bonds in PBLG sustain the α‐helical structure, giving the polymer a rodlike shape where the persistence length approaches 1000 Å. Third, past investigations of the effects of a once‐broken (or hinged) rod shape on intrinsic viscosity of polymer solutions and dielectric behavior relied on using a molecular hinge such as an alkyl amine that is flexible in nature and does not undergo photoisomerization 8–10. In contrast, the Az moiety has a rigid aromatic core that undergoes cis–trans isomerization.…”

Section: Introductionmentioning

confidence: 99%

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Incorporation of a photochromic hinge in a rodlike polypeptide and its influence on dielectric and optical properties

Williams¹,

Gupta²

2001

J Polym Sci B Polym Phys

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A hinged, photoresponsive polypeptide (PAzP) was prepared and the effect of the photochromic hinge on the dielectric and photoisomerization behavior of the polymer in solution was probed. Polymerization of N-carboxyanhydride of ␥-benzyl-Lglutamate was carried out with two different bifunctional photochromic amine initiators: di[(mercaptoethylamine)-methylpropanamide]azobenzene (DMMPAB) and diaminoazobenzene (DAAB). Careful structural comparison of the polymers revealed that the basicity of the initiator plays a key role in determining the shape and structure of the polymer. Specifically, the use of a novel initiator DMMPAB prepared by the addition of flexible aliphatic amine substituents onto DAAB resulted in a hinged polymer (PAzP1), in which a single photochromic hinge was located within the polymer chain (M w ϳ 36 kDa). In contrast, direct initiation with DAAB resulted in a polymer (PAzP2) in which the photochromic moiety was preferentially near the terminus of the polymer chain (M w ϳ 21 kDa) and the polymer possessed a significant degree of asymmetry. Dielectric spectroscopy revealed that, in spite of a higher molecular weight, PAzP1 had a lower rotational relaxation time (2.72 s) in solution than that of PAzP2 (4.41 s). The residual dipole moment for the hinged PAzP1 was also smaller than that observed for PAzP2. The hinged polypeptide PAzP1 prepared from DMMPAB showed uniform photoisomerization between cis and trans states. However, the presence of flexible aliphatic amine substituents on DMMPAB caused the rate of isomerization of PAzP1 to be similar to the initiator DMMPAB. Optical characterization revealed that heterogeneity in the structure of PAzP2 was manifested as nonuniform rates of photoisomerization and thermal relaxation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%