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Part?culas inteligentes de poli (nisopropilacrilamida), quitosana e poli (?cido acr?lico): efeito da temperatura e do pH sobre suas propriedades em suspens?es aquosasMarques, N?via do Nascimento 12 July 2012 (has links)
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Previous issue date: 2012-07-12 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present study describes the stability and rheological behavior of suspensions of
poly (N-isopropylacrylamide) (PNIPAM), poly (N-isopropylacrylamide)-chitosan (PNIPAMCS),
and poly (N-isopropylacrylamide)-chitosan-poly (acrylic acid) (PNIPAM-CS-PAA)
crosslinked particles sensitive to pH and temperature. These dual-sensitive materials were
simply obtained by one-pot method, via free-radical precipitation copolymerization with
potassium persulfate, using N,N -methylenebisacrylamide (MBA) as a crosslinking agent.
Incorporation of the precursor materials into the chemical networks was confirmed by
elementary analysis and infrared spectroscopy. The influence of external stimuli such as pH
and temperature, or both, on particle behavior was investigated through rheological
measurements, visual stability tests and analytical centrifugation. The PNIPAM-CS particles
showed higher stability in acid and neutral media, whereas PNIPAM-CS-PAA particles were
more stable in neutral and alkaline media, both below and above the LCST of poly (Nisopropylacrylamide)
(stability data). This is due to different interparticle interactions, as well
as those between the particles and the medium (also evidenced by rheological data), which
were also influenced by the pH and temperature of the medium. Based on the results obtained,
we found that the introduction of pH-sensitive polymers to crosslinked poly (Nisopropylacrylamide)
particles not only produced dual-sensitive materials, but allowed
particle stability to be adjusted, making phase separation faster or slower, depending on the
desired application. Thus, it is possible to adapt the material to different media / Esse estudo descreve a estabilidade e o comportamento reol?gico de suspens?es
aquosas de part?culas reticuladas sensitivas de poli (N-isopropilacrilamida) (PNIPAM), poli
(N-isopropilacrilamida)-quitosana (PNIPAM-QS) e poli (N-isopropilacrilamida)-quitosanapoli
(?cido acr?lico) (PNIPAM-CS-PAA). A obten??o dos materiais foi realizada por
polimeriza??o por precipita??o, via radicais livres, utilizando persulfato de pot?ssio como
iniciador e N,N -metilenobisacrilamida (MBA) como agente reticulante. A incorpora??o dos
precursores nas part?culas reticuladas foi confirmada por an?lise elementar e espectroscopia
na regi?o do infravermelho. A influ?ncia de est?mulos externos, como pH, temperatura, ou
ambos, no comportamento das part?culas, foi investigado por medidas reol?gicas, estabilidade
visual e centrifuga??o anal?tica. As part?culas de PNIPAM-QS apresentaram maior
estabilidade em meios ?cido e neutro, enquanto que as part?culas de PNIPAM-QS-PAA foram
mais est?veis em meios neutro e alcalino, tanto abaixo quanto acima da LCST da PNIPAM
(dados de estabilidade). Isso ocorreu devido ?s diferentes intera??es interpart?culas e entre as
part?culas e o meio (tamb?m evidenciadas pelos dados reol?gicos), que foi influenciada pelo
pH e temperatura do meio. Baseando-se nos resultados obtidos, observou-se que a introdu??o
de pol?meros sens?veis ao pH nas part?culas reticuladas de poli (N-isopropilacrilamida),
resultou n?o apenas na s?ntese de copol?meros reticulados com dupla sensibilidade, mas em
part?culas pass?veis de ajuste de estabilidade, ou seja, que podem sofrer separa??o de fases
mais ou menos r?pida, dependendo da aplica??o desejada. Dessa forma, ? poss?vel adaptar as
part?culas sintetizadas aos mais diversos meios
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Synthèse et caractérisation de copolymères stimulables à base de N,N-diéthylacrylamide / Synthesis and characterization of stimuliresponsive copolymers based on N,N-diethylacrylamideZhang, Xuewei 25 January 2010 (has links)
Ce travail de thèse concerne la synthèse et la caractérisation d'homo et de copolymères stimulables à base de N,N-diéthylacrylamide (DEAm). Des homopolymères ont été préparés par polymérisation radicalaire contrôlée par transfert réversible par addition-fragmentation (RAFT). Cette polymérisation a été conduite en présence de trois agents de transfert différents et s'est avérée contrôlée quelles que soient les conditions expérimentales. Deux types de copolymères ont ensuite été préparés, de type PEG-b-PDEAm et PDEAm-b-polypeptides par polymérisation RAFT et combinaison RAFT/ polymérisation par ouverture de cycle (ROP), respectivement. Ces copolymères double hydrophiles ont été caractérisés et leur comportement en solution aqueuse a été évalué. Nous avons montré la formation de micelles c?ur-couronne au dessus de la LCST. Nous avons également développé une stratégie de synthèse originale dans le cas des PDEAm-b-polypeptides puisque la ROP a été réalisée en utilisant un macroamorceur de type thiol. Après déprotection des copolymères sensibles au pH et à la température ont été obtenus et montre des propriétés de structuration différentes en fonction de ces deux stimuli. / This manuscript deals with the synthesis and characterization of responsive copolymers containing N,N-diethylacrylamide (DEAm). Homopolymers were prepared by controlled radical polymerization, especially Reversible Addition-Fragmentation Transfer (RAFT). Polymerization was achieved using three different chain transfer agents and was controlled whatever the experimental conditions. PEG-b-PDEAm and PDEAm-b-polypeptides were synthesized by RAFT polymerization and RAFT/Ring Opening Polymerization (ROP) respectively. These double hydrophilic block copolymers were characterized and their behavior in aqueous solution was evaluated. We showed that core/corona micelles were obtained above the lower critical solution temperature. We also developed a new strategy for the synthesis of PDEAm-b-polypeptides as ROP was achieved using a thiol macroinitiator. After deprotection pH- and thermo-sensitive copolymers were afforded which proved different structuration as a function of both stimuli.
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