ABSTRACT In this work, electrospun fibers of poly(butylene adipate-co-terephthalate)/poly(N-isopropylacrylamide), PBAT /PNIPAAm, and ecovio®/PNIPAAm blends were obtained. These blends presented a thermoresponsive behavior including a sudden response to temperature variation between 32 and 35 ºC. The addition of PNIPAAm to PBAT and ecovio® solutions significantly improved the electrospinability of both solutions as blends, allowing them to form rounded fibers without defects and with diameters varying between 1000 and 1700 nm. The analysis of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectra for PBAT/PNIPAAm and ecovio®/PNIPAAm electrospun fibers revealed that the electrospinning process does not lead to the formation of strong intermolecular interactions, such as hydrogen bonds, between the constituents of the studied blends’ electrospun fibers. Significant drop water contact angle variation as a function of temperature was observed for both PBAT/PNIPAAm and ecovio®/PNIPAAm electrospun fibers; both presented PNIPAAm’s hydrophilic-hydrophobic transition in the range between 32 and 35 ºC. Comparing PBAT/PNIPAAm and ecovio®/PNIPAAm electrospun fibers, the former was revealed to be more temperature-sensitive than the latter, regarding changes in wettability as the former presented larger gaps in drop water contact angle values compared to the latter. With these results, these blends in the form of electrospun fibers may have a potential application in the field of cell adhesion/detachment.

RESUMO Neste trabalho foram obtidas fibras eletrofiadas de blendas de Ecovio® e de poli(N-isopropilacrilamida) de alta massa molar (Ecovio®/PNIPAAm AMM) e de baixa massa molar (Ecovio®/PNIPAAm BMM). As fibras de blendas de Ecovio®/PNIPAAm AMM foram obtidas a partir de soluções com concentração de 10% e nas proporções mássicas de 100/0, 85/15, 70/30, 50/50 e 0/100. As fibras de Ecovio®/PNIPAAm BMM foram obtidas a partir de soluções de Ecovio® a 20% com adição 1%, 2%, 3% ou 10% de PNIPAAM BMM. As fibras eletrofiadas foram caracterizadas pelas técnicas de microscopia eletrônica de varredura (MEV), espectroscopia de infravermelho com transformada de Fourier usando acessório de reflectância atenuada (FTIR-ATR) e de medidas de molhabilidade das superfícies das fibras em função da temperatura. Verificou-se que a adição de PNIPAAm AMM às soluções das blendas de Ecovio®/PNIPAAm favoreceu a eletrofiabilidade das soluções, pois as fibras obtidas apresentaram morfologia esférica e ausência de contas, principalmente a partir da proporção mássica de PNIPAAm AMM de 30%. Além disso, a presença de PNIPAAm AMM tornou as fibras de Ecovio®/PNIPAAm termossensíveis. Esse resultado foi observado a partir das medidas de ângulo de contato da gota de água em função da temperatura, que mostraram que a molhabilidade dessas fibras aumentou em temperaturas abaixo de 32 oC e, em temperaturas acima de 32 oC, a molhabilidade diminuiu. Isso ocorreu devido à transição hidrofílica-hidrofóbica, característica do PNIPAAm na faixa de 32-35 °C. Por outro lado, não foi verificado o mesmo comportamento para as fibras de Ecovio®/PNIPAAm BMM, as quais tiveram uma melhora na molhabilidade com a adição de PNIPAAm BMM, mas não apresentaram o comportamento de termosssensiblidade, provavelmente devido ao menor tamanho das cadeias do PNIPAAm BMM, que não favoreceu a transição hidrofílica-hidrofóbica. Assim, provavelmente apenas as fibras eletrofiadas de Ecovio®/PNIPAAm AMM poderiam vir a apresentar potencial aplicação na área de crescimento/descolamento celular.

ABSTRACT In this work were obtained electrospun fibers from Ecovio® and poly (N-isopropylacrylamide) high molar mass (Ecovio®/PNIPAAm AMM) and low molar mass (Ecovio®/PNIPAAm BMM) blends. Ecovio®/PNIPAAm AMM blend fibers were obtained from solutions with a concentration of 10% and in the mass ratios of 100/0, 85/15, 70/30, 50/50 and 0/100. Ecovio®/PNIPAAm BMM fibers were obtained from 20% Ecovio® solutions with 1%, 2%, 3% or 10% addition of PNIPAAM BMM. The electrospun fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy using attenuated reflectance enhancement (FTIR-ATR) and fiber surface wettability measurements. The addition of PNIPAAm AMM to the solutions of Ecovio®/PNIPAAm blends favored the electrospinning of the solutions, since the fibers obtained showed spherical morphology and absence of beads, mainly from the 30% mass ratio of PNIPAAm AMM. In addition, the presence of PNIPAAm AMM made Ecovio®/PNIPAAm fibers thermosensitive. This result was observed from water drop contact angle measurements as a function of temperature, which showed that the wettability of these fibers increased at temperatures below 32 ºC and at temperatures above 32 ºC decreased. This was due to the hydrophilic-hydrophobic transition characteristic of PNIPAAm in the 32-35 °C range. On the other hand, the same behavior was not observed for the Ecovio®/PNIPAAm BMM fibers, which had an improvement in wettability with the addition of PNIPAAm BMM, but did not exhibit the thermosensitivity behavior, probably due to the smaller size of the PNIPAAm BMM chains, which did not favor the hydrophilic-hydrophobic transition. Thus, it is likely that only the electrospun Ecovio®/PNIPAAm AMM fibers could have potential application in the area of cell growth/detachment.