NIPAM radical polymerization

N-isopropylacrylamide (NIPAM) monomer (courtesy of Kohjin Ltd) can be purified by re-crystallization in a benzene/n-hexane mixture and azobi-sisobutyronitrile (AIBN) (from Aldrich, analytical grade) can also be purified by re-crystallization. In a typical free-radical polymerization, 18 g NIPAM monomer was first dissolved in 150 mL benzene with 1 mol % of AIBN added as the initiator. The solution mixture was then degassed through three cycles of freezing and thawing. Polymerization was carried out in an oil bath at 56 °C for 30 h under a positive nitrogen pressure. The solvent was removed... 

Comonomer l-vinyl-2-pyrrolidone (VP) comonomer can be purified by distillation at reduced pressure prior to use. Potassium persulfate (KPS) can be purified in a mixture of water and methanol. NIPAM-co-VP copolymers with different amounts of VP can be prepared at temperatures lower or higher than the LCST of PNIPAM by free radical polymerization in water with an initiator of KPS/N,N,N/,N/-tetramethylethylenediamine (TEMED) redox. The resultant copolymer can be harvested by precipitation, i.e., pouring the reaction mixture into an equal volume of methanol. Each resultant copolymer can be further purified by several cycles of re-dissolution in water and precipitation in methanol to ensure a complete removal of residual monomers. The final product can be dried under reduced pressure at 40 °C. 

Thermally responsive polymers, such as poly( V-isopropyl acrylamide) (NI-PAm), have also been studied extensively for applications related to those previously discussed [112], De las Heras et al. described the synthesis and patterning of NIPAm brushes on SAMs and their subsequent performance during temperature-dependent adhesion assays of BSA and Streptococcus mutans (Fig. 7). The authors employed p.CP to pattern features of hydrophobic hexadecanethiol and backfilled the surface with an initiator-functionalized alkanethiol. Polymer brushes were grown via surface-initiated atom transfer radical polymerization (ATRP). FITC-BSA was then... 

Heterobifiinctional block copolymers of PEO and poly (N-isopropylacrylamide) (PNIPAM) were synthesized by RAFT polymerization of N-isopropylacrylamide (NIPAM) using a PEO-based trithiocarbonate macromolecular CTA. The polymerization exhibited all the expected characteristics of living radical polymerization and allowed the synthesis of copolymers with different lengths of the PNIPAM block. 

The PLP-SEC investigations into kp of free-radical polymerization in aqueous phase suggest that kp varies strongly with monomer concentration. For MAA, NIPAm ) and AAm a strong decrease in kp was found upon increasing monomer concentration. The same trend is seen for AA from monomer concentrations of 3 wt.-% on, whereas at very low AA contents kp increases with acrylic acid concentration. Attempts to assign the strong solvent effects to associated struc-tures, ) to dimerization,f l or to local monomer concentrations at the radical site... 

Using such process and such batch radical polymerization process, various thermally sensitive hydrogels have been elaborated using NIPAM, NIPMAM, NEMAM, and more recently A-vinyl caprolactam (VCL)-based microgels [7-10]. 

The versatility of the radical polymerization mechanism of NIPAM and VCL provides straightforward access to a wide range of copolymers based on the large variety of vinyl monomers that are commercially available. As such, the Tcp of PNIPAM and VCL can be easily controlled and tuned by the preparation of statistical copolymers with inert comonomers having higher or lower hydrophilicity to increase or decrease the CP> respectively... 

In this paper, the living radical polymerization of N-isopropylacrylamide (NIPAM) and the living cationic polymerization of vinyl ethers having oxyethylene groups are outlined (Fig. 1), as they constitute a new wave of the... 

Development of Living Radical Polymerization and Radical Polymerization of NIPAM... 

Numerous reports describing the successful RAFT polymerization of NIPAM have appeared [35]. For example, in 2000, Rizzardo et al. first reported the RAFT living radical polymerization of NIPAM by AIBN employing benzyl dithiobenzene or cumyl dithiobenzoate RAFT agents 1 (Fig. 2) [39]. Fukuda et al. synthesized block copolymers using these systems [40]. Subsequently,... 

The establishment of the living radical polymerization of NIPAM encouraged not only many polymer chemists but also polymer physicists to prepare functionalized NIPAM polymers with various controlled sequences and/or shapes, as discussed in this chapter. In the following parts, block, random, or graft copolymers will be simply designated by the acronym A-B for a diblock copolymer, A-B-A for an ABA-type triblock copolymer, A-B-C for an ABC-type triblock copolymer, A-co-B for a random copolymer, A-g-PNIPAM for grafting of NIPAM segments onto the polymer A. For example, PNIPAM-PEO stands for a diblock copolymer of PNIPAM and PEO. 

In other endeavors to prepare NIPAM nanoparticles, the introduction of NIPAM brushes onto fine particles [146] or NIPAM nanotubes [147] has been attempted. Furthermore, Kawaguchi et al. have prepared various types of thermoresponsive hair particles by Hving radical polymerization using the photoiniferter method [148-150]. These particles demonstrated cer-... 

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