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The fabrication of a new copper-functionalized lignocellulosic microreactor (Cu-LμR) from bamboo culms is herein described together with its operation to perform a copper­(I)-catalyzed 1,3-dipolar cycloaddition between azide and terminal alkyne (CuAAC). The bio-microfluidic device showed an easy prototyping and fast functionalization with copper ions. All reactions were carried out in flow regime with aqueous-methanol solvent and minimal leaching of copper, yielding a series of model 1,4-disubstitued triazole derivatives with good efficiency in a low-resource setting.

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This article presents a molecular dynamics study performed by combining conventional and fast-field cycling NMR relaxation techniques in nanocomposite systems for the optimization of drug delivery systems. The biodegradable polymers polycaprolactone, polylactide, polyvinyl alcohol and maize starch were used as base polymers and they were modified by incorporation of nanoparticles and/or cross-linking reactions, in order to understand the interaction between the bioactive molecules and the supporting matrix for a controlled drug release. Nevirapine was used as a testing bioactive drug. H spin-lattice relaxation times were measured for Larmor frequencies between 10 kHz and 300 MHz to obtain information about molecular motions in different time scales for comprehensive analysis of the possible interactions of the polymer matrices, modified nanoparticles and bioactive molecules. All systems presented some degree of crystallinity and poly-exponential decay of magnetization in the spin-lattice relaxation. The shortest spin-lattice relaxation times were assigned to the more amorphous regions and the relaxation dispersion was similar to that found in polymer melts. The effects of both nanoparticles and bioactive molecules on the molecular dynamics of the polymer matrices were clearly detected. The results show that NMR relaxometry study covers a broad range of frequencies and it is a powerful and suitable method to characterize nanocomposite systems at the molecular scale, provides information about the mobility of polymer chains and the strength of the interaction between polymers/nanoparticles. This information helps to make inferences about drug confinement level inside the systems, which can have a direct influence on the drug release. It is extremely important to know the exact drug release mechanism of bioactive molecules in a medical treatment. The main results indicated that the NMR techniques used were able to evaluate the molecular dynamics of the nanocomposites studied. It can be pointed out that PCL/clay nanocomposites containing nevirapine drug, caused a compensating effect regarding to the distribution of correlation times for the molecular segment motions and the drugs interferes in the nanomaterial molecular dynamics.

IntroduçãoPoliuretanos (PUs) são polímeros utilizados na fabricação de elastômeros, propelentes, agentes encapsulantes, e em diversos setores como: construção, embalagens, equipamentos, livros, calçados, moveleiro, medicina, eletro-eletrônico, aeroespacial, automotivo, abrasivos, têxteis e outros [1] . Uma importante área de utilização desse material é na fabricação de adesivos, uma vez que, os PUs se unem a maioria dos materiais sob a forma de adesivos eficientes, resistentes à vibração e, são aplicáveis em ampla faixa de temperatura [2] . Outra aplicação interessante é no desenvolvimento de membranas, que além de separarem efetivamente misturas de gases, como CO 2 e N 2 , podem ser utilizadas em recuperação de CO 2 do petróleo, remoção de hélio do gás natural e recuperação de H 2 da corrente do gás de purga da planta de amônia, dentre outras [3][4][5][6][7] . A grande aplicabilidade dos polímeros de poliuretano deve-se à versatilidade estrutural do PU possibilitar a escolha de uma ampla gama de diisocianatos e polióis como monômeros [8,9] . A incorporação de nanocargas à matriz polimérica de PU pode diversificar ainda mais a utilização destes polímeros, pois a formação de nanocompósitos de PU tem mostrado melhoria de propriedades mecânicas, térmicas, de barreira, retardância de chama e estabilidade dimensional, quando comparados aos compósitos convencionais. Isto ocorre devido à boa dispersão das nanocargas e interação com a matriz de PU [9][10][11][12][13] . A caracterização de um material é a forma de entender a relação da sua estrutura com as propriedades que ele apresenta. No caso específico dos nanocompósitos poliméricos, é muito importante determinar a interação da matriz polimérica com a nanocarga; a dispersão homogênea desta nanocarga na matriz polimérica e formação de domínios de mobilidades distintas.Na literatura, a caracterização estrutural dos nanocompósitos poliméricos é normalmente feita pela espectroscopia de absorção na região do infravermelho. A caracterização da cristalinidade da fração argila e do polímero (quando este não é amorfo) é obtida pela difração de raios X; enquanto a microscopia eletrônica de transmissão mostra a dispersão das nanocargas, e as análises térmicas mostram as variações térmicas sofridas pelos novos Characterization of Polyurethane/Organophilic Montmorilonite Nanocomposites by Low Field NMRAbstract: Polyurethanes are important and versatile materials, mainly due to some of their properties, such as high resistance to abrasion and tearing, excellent absorption of mechanical shocks and good flexibility and elasticity. However, they have some drawbacks as well, such as low thermal stability and barrier properties. To overcome these disadvantages, various studies have been conducted involving organophilic polyurethane/montmorillonite nanocomposites. The investigation of the structure of polyurethane/clay nanocomposites has mainly been done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In this work, PU/clay nanocomposite films obtained by solution...