PNIPAAm acrylamide

Poly(A-isopropyl acrylamide) (PNIPAAm) is the most extensively studied temperature-sensitive polymer [10-20]. Crosslinked PNIPAAm exhibits drastic swelling transition at its lower critical solution temperature... 

The temperature-sensitive poly(A-isopropyl acrylamide) and pH-sensitive poly(methacrylic acid) were used as the two component networks in the IPN system. Since both A-isopropyl acrylamide (NIPAAm) (Fisher Scientific, Pittsburgh, PA) and methacrylic acid (MAA) (Aldrich, Milwaukee, Wl) react by the same polymerization mechanism, a sequential method was used to avoid the formation of a PNIPAAm/PMAA copolymer. A UV-initiated solution-polymerization technique offered a quick and convenient way to achieve the interpenetration of the networks. Polymer network I was prepared and purified before polymer network II was synthesized in the presence of network I. Figure I shows the typical IPN structure. 

Many recent studies on polymer gels are related to volume phase transition phenomena of poly(acrylamide) PAAm gel [7] and poly(N-isopropyl acrylamide) PNIPAAm gel [8, 9]. The volume phase transition in gels was extensively studied by Tanaka and his coworkers [10, 11]. 

Poly(amino acid)s (PAAs) have also been used in drug delivery PEO-(l-aspartic acid) block copolymer nano-associates , formed by dialysis from a dimethyl acetamide solution against water, could be loaded with vasopressin. PLA-(L-lysine) block copolymer microcapsules loaded with fluorescently labelled (FITC) dextran showed release profiles dependent on amino acid content. In a nice study, poly(glutamate(OMe)-sarcosine) block copolymer particles were surface-grafted with poly(A-isopropyl acrylamide) (PNIPAAm) to produce a thermally responsive delivery system FITC-dextran release was faster below the lower critical solution temperature (LCST) than above it. PAAs are prepared by ring-opening polymerisation of A-carboxyanhydride amino acid derivatives, as shown in Scheme 1. 

Pareek P, Adler H-J P, Kuckling D (2006) Tuning the swelling behavior of chemisorbed thin PNIPAAm hydrogel layers by N, N-dimethyl acrylamide content. Prog Colloid Polym Sci 132 145-151... 

PNIPAAm Poly(N-isopropyl acrylamide) PVA Poly (vinyl alcohol)... 

Alternatively, PNIPAAm was grafted on to aligned MWCNTs, generating a smart surface with thermal-responsive suprahydrophilic and suprahydropho-bic transition behavior.CNT-initiated ATRP of another acrylamide class of monomers has rarely reported yet, leaving space for the future work. Preparation of smart nanomaterials with both temperature and pH responsibility and exploration of the application of the smart nanowires are especially expected. 

Poly(N-isopropyl acrylamide) (PNIPAAm) is one of the most widely studied temperature sensitive polymers that undergoes clear solution to precipitation. However, its nonbiodegradabihty and concern for residual monomer toxicity limit the biomedical applications. To improve the problems, biodegradable... 

Besides the most typical PNIPAAm in the family of poly(A-substituted acrylamide), there are many other polymers (Fig. 9.4) that show varied transition properties in response to temperature changes. For example, poly(A, Af -diethyl acrylamide) (PDEAAm) has an LCST in the range of 25-32 °C [4], poly[A-(D,L)-(l-hydroxymethyl) propylmethacrylamide] (PDL-HMPMA) has one close to 35 °C... 

Porous silica supports such as MCM-41 have also been employed in the development of artificial hybrid pores due to their well-defined porous network and then-facile functionalization chemistry. For instance, Lopez and coworkers employed an MCM-41 support coated uniformly with a temperature-responsive poly(AI-isopropyl acrylamide) (PNIPAAm) polymer. At low temperatures, the polymer was hydrated and extended and the pores were closed no transport of fluorescein was observed when flow cytometry and confocal laser scanning microscopy were employed. In contrast, at high temperatures the polymer was hydrophobic and collapsed, allowing the transport of the dye (Figure 24). This system thus not only acts as a temperature sensor but also shows clear features of control as will become more important in the next section. 

Figure 7.10 Poly (A -substituted acrylamide) showing a LCST (a) Poly (iV-isopro-pylaciylamide) (PNIPAAm) (b) Poly(AyV-diethylacrylamide) (PDEAAm) (c) Poly(2-carboxyisopropylacrylamide) (PCIPAAm) (d) Poly(A -(Z) (l-hydroxymethyl), pro-pylmethacrylamide (P(Z-HMPMAAm)) (e) Poly(A - acryloyl-A/ -alkylpiperazine) [124]...

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