Copolymer-based microgels

On the other hand, in the hydrogenation of DMEC and DHL these catalysts are much less active and selective than PS-l)-P4VP-Pd or PEO-h-P2VP-Pd. The lower activity may be due to the formation of comparatively large particles (compare 2nm nanoparticles in block copolymer-based catalysts and the nanoparticles formed in microgel-templated catalysts). The lower selectivity can be caused by the absence of modifying groups on the nanoparticle surface. 

Fig. 16 The thermal response of different polymeric structures based on PVCL and the amphiphilic macromonomer MAC11EO42. Left Shrinking of the grafted PVCL microgel. Right Heat-induced aggregation of the graft copolymer and formation of a mesoglobule [181]...

Different architectures, such as block copolymers, crosslinked microparticles, hyperbranched polymers and dendrimers, have emerged (Fig. 7.11). Crosslinked microparticles ( microgels ) can be described as polymer particles with sizes in the submicrometer range and with particular characteristics, such as permanent shape, surface area, and solubility. The use of dispersion/emulsion aqueous or nonaqueous copolymerizations of formulations containing adequate concentrations of multifunctional monomers is the most practical and controllable way of manufacturing micro-gel-based systems (Funke et al., 1998). The sizes of CMP prepared in this way vary between 50 and 300 nm. Functional groups are either distributed in the whole CMP or are grafted onto the surface (core-shell, CS particles). 

Monodisperse microgels based on poly(acrylamide-methacrylic acid) copolymer [P(AAm-co-MAAc)] crosslinked by BIS with a sharp pH-induced volume transition were prepared in ethanol [68], Osmotic pressure and deformation of crosslinked polymer network were considered to be the two dominant factors influencing the... 

Copolymer microgel systems based on VCL were reported recently. Peng and Wu [71] reported synthesis of poly(V-vinylcaprolactam-co-sodium acrylate) microgels and Boyko et al. [72] synthesized microgels based on polyW-vinylcaprolactam-ro-iV-vinylpyrrolidonc). 

In the meantime, this phenomenon has also been observed by other groups for thermosensitive polymer-based metal nanoparticles [77, 78]. Pich et al. have used microgel particles based on the copolymer of A-vinylcaprolactam (VCL) and ace-toacetoxyethyl methacrylate (AAEM) (PVCL/PAAEM) as the carrier system for the deposition of metal nanoparticles. The microgels were first modified with poly(3,4-ethylenedioxythiophene) (PEDOT) nanorods through an in situ oxidative polymerization process. Microgels with PEDOT nanorods in the shell were then used for the... 

Becker et al. [64] functionalized a peptide, based on the protein transduction domain of the HIV protein TAT-1, with an NMP initiator while on the resin. They then used this to polymerize f-butyl acrylate, followed by methyl acrylate, to create a peptide-functionahzed block copolymer. Traditional characterization of this triblock copolymer by gel permeation chromatography and MALDI-TOF mass spectroscopy was, however, comphcated partly due to solubility problems. Therefore, characterization of this block copolymer was mainly hmited to ll and F NMR and no conclusive evidence on molecular weight distribution and homopolymer contaminants was obtained. Difficulties in control over polymer properties are to be expected, since polymerization off a microgel particle leads to a high concentration of reactive chains and a diffusion-limited access of the deactivator species. The traditional level of control of nitroxide-mediated radical polymerization, or any other type of controlled radical polymerization, will therefore not be straightforward to achieve. 

Copolymer microgels based on the same temperature-sensitive moieties as the core-shell systems discussed above have distinctly different behaviors. When the temperature-dependent hydrodynamic radius is determined, only one volume phase transition is observed SANS, however, is... 

Much of the work reported in the academic literature is based upon microgels prepared from poly(NIPAM), but there are, however, a number of microgels that have been prepared from other monomers. These include methyl methacrylate with other copolymers such as ethylene glycol dimethacrylate (17,18), methyl methacrylate with p-divinylbenzene (19), and methyl methacrylate with methacrylic acid (20). Other microgel particles have been prepared from poly(allylamine hydrochloride) (21), vinylpyrrolidinone and acrylic acid (22), acrylamide and acrylamide with methacrylamidopropyltrimethylammonium chloride (23), and acrylamide copolymerized with 2-acrylamido-2-methylpropanesulfonic acid (24). 

The microgel particles used in present study are based on copolymer of vinylcaprolactam (VCL) and acetoace-toxye yl methacrylate (AAEM). As described in our previous studies the microgel particles possess heterogeneous stmcture and consist of AAEM-rich core and VCL-rich shell due to some peculiarities of the polymerization process [30], The use of small fraction of vinylimidazole (Vim) during VCL/AAEM microgel synthesis allows selective incorporation of Vim units in the... 

---