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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
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17684 |
| Date | 12 July 2012 |
| Creators | Marques, N?via do Nascimento |
| Contributors | CPF:65946499734, http://lattes.cnpq.br/7711521318854102, Bicudo, Tatiana de Campos, CPF:25935096862, http://lattes.cnpq.br/2712586287719863, Santos, Am?lia Severino Ferreira e, CPF:59284064104, http://lattes.cnpq.br/5119417295487126, Villetti, Marcos Antonio, CPF:49242172049, http://lattes.cnpq.br/8504489050993642, Balaban, Ros?ngela de Carvalho |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Qu?mica, UFRN, BR, F?sico-Qu?mica; Qu?mica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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