A Modular Approach toward Block Copolymers

Abstract

A novel methodology for the formation of block copolymers has been developed that combines ring-opening metathesis polymerization (ROMP) with functional chain-transfer agents (CTAs) and self-assembly. Telechelic homopolymers of cyclooctene derivatives end-functionalized with hydrogen-bonding or metal-coordination sites are formed through the combination of ROMP with a corresponding functional CTA. These telechelic homopolymers are fashioned with a high control over molecular weight and without the need for post-polymerization procedures. The homopolymers undergo fast and efficient self-assembly with their complement homopolymer or small molecule analogue to form block-copolymer architectures. The block copolymers show equivalent association constants as their small molecule analogues described in the literature, regardless of size or nature of the complementary unit or the polymer side chain.

Propriedades fotoquímicas e fotofísicas, e investigação teórica de um novo monômero-complexo de Ru(II)-bipiridina

“…The occurrence of a 3Amnpy-loss reaction is expected, since a similar reaction has been observed for related Ru complexes, such as cis-[Ru(bpy) 2 L 2 ] (L ) py; and substituted pyridines). 26 For these complexes, the efficiency of the photoreaction appeared to depend on the substitution of pyridine and on the energy difference between the MLCT and MC states. 26 The photoreaction was therefore proposed to proceed from the lowest MC state, after surface crossing from the MLCT states.…”

“…26 For these complexes, the efficiency of the photoreaction appeared to depend on the substitution of pyridine and on the energy difference between the MLCT and MC states. 26 The photoreaction was therefore proposed to proceed from the lowest MC state, after surface crossing from the MLCT states. 26 This is associated with the chelating nature of the 3Amdpy 2 oxaNBE ligand present in 2.…”

“…26 Thus, a possible explanation for the spectral changes would be a simple 3Amnpy photosolvation to form cis-[Ru- (bpy) 2 28 Therefore, it might be labile in metal complexes with low-energy MC excited states, as in the case of Ru(II) hexacoordinate complexes. 26 In contrast, complex 2 appers to be photochemically unreactive.…”

“…26 Thus, a possible explanation for the spectral changes would be a simple 3Amnpy photosolvation to form cis-[Ru- (bpy) 2 28 Therefore, it might be labile in metal complexes with low-energy MC excited states, as in the case of Ru(II) hexacoordinate complexes. 26 In contrast, complex 2 appers to be photochemically unreactive. No detectable UV-vis spectral changes could be observed after 2 h. The lack of photoreaction in solution for complex 2 is a consequence of the chelate ring of 1, which contributes to the stability of the complex 2 under continuous light irradiation.…”

“…Muito progresso tem sido alcançado no desenvolvimento de metalopolímeros contendo o metal com o macroligante [25,26]. Entretanto, ainda se faz necessário que novas metodologias sejam estabelecidas para o preparo de ligantes funcionalizados tais como monômeros funcionalizados [27] e ligações destes aos metais.…”