http://www.mdpi.com/journal/polymers/special_issues/advanced-architectures/ {snippet name="submission_info"} http://www.mdpi.com/2073-4360/2/4/623/ We found novel photo-induced micellizations through photolysis, photoelectron transfer, and photo-Claisen rearrangement. The photolysis-induced micellization was attained using poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light scattering demonstrated that the copolymer produced spherical micelles in this solvent due to irradiation with a high-pressure mercury lamp in the presence of photo-acid generators, such as bis(alkylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, and triphenylsulfonium triflate. The 1H NMR analysis confirmed that PBSt-b-PSt was converted into poly(4-vinylphenol)-block-PSt by the irradiation, resulting in self-assembly into micelles. The irradiation in the presence of the photo-acid generator also induced the micellization of poly(4-pyridinemethoxymethylstyrene)-block-polystyrene diblock copolymer (PPySt-b-PSt). Micellization occurred by electron transfer from the pyridine to the photo-acid generator in their excited states and provided monodispersed spherical micelles with cores of PPySt blocks. Further, the photo-Claisen rearrangement caused the micellization of poly(4-allyloxystyrene)-block-polystyrene diblock copolymer (PASt-b-PSt). Micellization was promoted in cyclohexane at room temperature without a catalyst. During micellization, the elimination of the allyl groups competitively occurred along with the photorearrangement of the 4-allyloxystyrene units into the 3-allyl-4-hydroxystyrene units. http://www.mdpi.com/2073-4360/2/4/623/ Fri, 26 Nov 2010 00:00:00 CET Polymers 2010-11-26 2 4 Review 623 648 2073-4360 Photo-Induced Micellization of Block Copolymers 2010-11-26 doi: 10.3390/polym2040623 Eri Yoshida Satoshi Kuwayama http://www.mdpi.com/2073-4360/2/4/418/ New polymers were synthesized from α-hydroxy acids derived from the natural amino acids Ile, Leu, Phe, and Val, combined with lactic acid, glycolic acid and 6-hydroxyhexanoic acid by direct condensation. The toxicity was determined and the degradation process of these polyesters was investigated under physiological conditions by analyzing the composition of the degraded polymers and the oligomers cleaved in the buffer medium. The polymers were found to be non toxic to two cell lines. Polymers displayed a biphasic degradation behavior. In most cases, a linear relationship was found between the weight loss constant and the hydrophobicity of the polymers, Log P. Regarding the second stage of weight loss, it is apparent that polymers derived from α-hydroxy(L)isoleucine ((L)HOIle) and α-hydroxy(L)Valine ((L)HOVal) degraded much faster than those derived from α-hydroxy(L)leucine ((L)HOLeu) and α-hydroxy(L)phenylalanine ((L)HOPhe), probably due to different spatial orientation of the side chains. Copolymers of 6-hydroxyhexanoic acid displayed slow degradation rates as expected, whereas the degradation profile of copolymers of lactic acid was similar to the other homopolymers. These new polyesters may serve as potential biocompatible materials for medical applications. http://www.mdpi.com/2073-4360/2/4/418/ Wed, 13 Oct 2010 00:00:00 CEST Polymers 2010-10-13 2 4 Article 418 439 2073-4360 New Biocompatible Polyesters Derived from α-Amino Acids: Hydrolytic Degradation Behavior 2010-10-13 doi: 10.3390/polym2040418 Naomi Cohen-Arazi Abraham J. Domb Jeoshua Katzhendler http://www.mdpi.com/2073-4360/2/4/364/ Thermal decomposition of alkoxyamines in the presence of scavengers was found to proceed with the formation of chemically induced nuclear polarization detected by 1H NMR. The distinctive Chemically Induced Dynamic Nuclear Polarization (CIDNP) features were studied using the example of three alkoxyamines: 4-nitrophenyl 2-(2,2,6,6-tetramethylpiperidin-1-yloxy)-2-methylpropanoate (1a), 4-nitrophenyl 2-(2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxy)-2-methylpropanoate (2a) and 4-nitrophenyl 2-(2,2,5,5-tetramethyl-4-phenyl-2H-imidazol-1-oxy)-2-methylpropanoate (3a) in the presence of PhSH. The analysis of CIDNP signs of methacrylate protons allows us to conclude on the occurrence of hydrogen atom transfer reaction in geminate radical pair formed in alkoxyamine thermolysis. Thus, CIDNP is a fast and sensitive method to detect the occurrence of intra/intermolecular hydrogen transfer in alkoxyamine thermolysis. http://www.mdpi.com/2073-4360/2/4/364/ Tue, 28 Sep 2010 00:00:00 CEST Polymers 2010-09-28 2 4 Article 364 377 2073-4360 Chemically Induced Dynamic Nuclear Polarization during the Thermolysis of Alkoxyamines: A New Approach to Detect the Occurrence of H-Transfer Reactions 2010-09-28 doi: 10.3390/polym2040364 Maria Edeleva Sylvain R. A. Marque Denis Bertin Didier Gigmes Yohann Guillaneuf Elena Bagryanskaya http://www.mdpi.com/2073-4360/2/3/353/ The rate constants kd of the homolysis of the C–ON bond in styryl dyads TEMPO-based alkoxyamines have recently been published (Li et al. Macromolecules 2006, 39, 9201). The diastereoisomers exhibited different values which were higher than for the unimer TEMPO-styryl alkoxyamine 1. At a first glance, the localization of the steric strain was not obvious. To decipher this problem, diastereoisomer models 2 (RR/SS) and 3 (RS/SR), as well as the released alkyl radicals, were calculated at the \B3LYP/6-31G(d) level. It was revealed that the increase in kd from 1 to 3 was due to the compression (buttressing effect) of the reactive center by the second styryl moiety. The difference in kd for the diastereoisomer was clearly an activation entropy effect DS≠ because the alkyl fragment of the RS/SR diastereoismer exhibited the same conformation as the released radical whereas the conformation for the RR/SS diastereoisomer was quite different and thus required the rotation of several bonds to reach the correct TS, which cost DS≠, and thus lowers kd. http://www.mdpi.com/2073-4360/2/3/353/ Mon, 27 Sep 2010 00:00:00 CEST Polymers 2010-09-27 2 3 Article 353 363 2073-4360 Diasteromeric Effect on the Homolysis of the C–ON Bond in Alkoxyamines: A DFT Investigation of 1,3-Diphenylbutyl-TEMPO 2010-09-27 doi: 10.3390/polym2030353 Alexandra Blachon Sylvain R. A. Marque Valérie Roubaud Didier Siri