@article {2473, title = {Poly(oligo(ethylene glycol)acrylamide) Brushes by Surface Initiated Polymerization: Effect of Macromonomer Chain Length on Brush Growth and Protein Adsorption from Blood Plasma}, journal = {Langmuir}, volume = {25}, number = {6}, year = {2009}, note = {ISI Document Delivery No.: 418JRTimes Cited: 12Cited Reference Count: 45Kizhakkedathu, Jayachandran N. Janzen, Johan Le, Yevgeniya Kainthan, Rajesh K. Brooks, Donald E.}, month = {Mar}, pages = {3794-3801}, type = {Article}, abstract = {Three hydrolytically stable polyethyleneglycol (PEG)-based N-substituted acrylamide macromonomers, methoxypolyethyleneglycol (350) acrylamide (MPEG(350)Am) methoxypolyethyleneglycol (750) acrylamide(MPEG(750)Am) and methoxypolyethyleneglycol (2000)acrylamide (MPEG(2000)Am) with increasing PEG chain length were synthesized. Surface-initiated aqueous atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10-hexamethyl triethylene tetramine (HMTETA) catalyst was utilized to generate dense polymer brushes from these monomers via an ester linker group on the surface of model polystyrene (PS) particles. The molecular weight, hydrodynamic thickness, and graft densities of the grafted polymer layers were controlled by changing the reaction parameters of monomer concentration, addition of Cu(II)Cl-2, and sodium chloride. The graft densities of surface-grafted brushes decreased with increasing PEG macromonomer chain length, 350 > 750 >> 2000, under similar experimental conditions. The molecular weight of grafts increased with increase in monomer concentration, and only selected conditions produced narrow distributed polymer chains. The molecular weight of grafted polymer chains differs significantly to those formed in solution. The hydrodynamic thicknesses of the grafted polymer layers were fitted to the Daoud and Cotton model (DCM) for brush height on spherical surfaces. The results show that the size of the pendent groups on the polymer chains has a profound effect on the hydrodynamic thickness of the brush for a given degree of polymerization. The new PEG-based surfaces show good protection against nonspecific protein adsorption from blood plasma compared to the bare surface. Protein adsorption decreased with increasing surface density of grafted polymer chains. Poly(MPEG(750)Am) brushes were more effective in preventing protein adsorption than poly(MPEG(350)Am) even at low graft densities, presumably due to the increase in PEG content in the grafted layer.}, keywords = {AQUEOUS ATRP, COPOLYMER BRUSHES, density, METHYL-METHACRYLATE, MODEL, N-DIMETHYLACRYLAMIDE), OLIGO(ETHYLENE GLYCOL) METHACRYLATE, PHOSPHORYLCHOLINE, POLY(N, POLYMERS, TRANSFER RADICAL POLYMERIZATION}, isbn = {0743-7463}, url = {://000264145000068}, author = {Kizhakkedathu, J. N. and Janzen, J. and Le, Y. and Kainthan, R. K. and Brooks, D. E.} } @article {2342, title = {A novel functional polymer with tunable LCST}, journal = {Macromolecules}, volume = {41}, number = {14}, year = {2008}, note = {ISI Document Delivery No.: 326NJTimes Cited: 13Cited Reference Count: 44Zou, Yuquan Brooks, Donald E. Kizhakkedathu, Jayachandran N.}, month = {Jul}, pages = {5393-5405}, type = {Article}, abstract = {Poly(N-[(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide) (PDMDOMA), a novel thermo-responsive polymer containing pendant dioxolane groups was synthesized via atom transfer radical polymerization (ATRP). Water soluble PDMDOMAs with controlled molecular weight and narrow molecular weight distribution were obtained. GPC-MALLS and MALDI-TOF-MS analysis verified the controlled nature of polymerization. It was found that an aqueous solution of PDMDOMA has a lower critical solution temperature (LCST) around 23 degrees C. The LCST of PDMDOMA was finely tuned over a wide temperature range by the partial hydrolysis of the acid labile dioxolane side group to form diol moieties (PDMDOMA diols). Unlike the traditional way of controlling LCST by copolymerization, the advantage of this method is that a series of thermo-responsive polymers with different LCST can be prepared from a single batch of polymer with comparable molecular weight profiles. The LCST of the resulting PDMDOMA diols increased almost linearly up to 28 mol \% of diol in the copolymer and the LCST disappeared above 43 mol \% diol content. The diol moiety generated during the hydrolysis was further oxidized to create aldehyde functionalities along the polymer backbone (PDMDOMA-aldehyde). The NMR analysis indicates that the aldehyde groups in the polymer exist in equilibrium with their covalent hydrates in water. The presence and reactivity of aldehyde groups on the PDMDOMA-aldehyde was verified by reaction with propylamine and aniline. The LCST of PDMDOMA-aldehyde did not change significantly compared to the precursor diol polymer. However, the propylamine or aniline derivatives showed a dramatic decrease in the LSCT possibly due to an increase in the hydrophobic character. The LCST of PDMDOMA-propylamine and PDMDOMA-aniline derivatives depends on the composition and nature of the attached groups. The structure of PDMDOMA and its derivatives were fully characterized by H-1, C-13, and 2D HMQC NMR, GPC-MALLS, and MALDI-TOF-MS.}, keywords = {2-(2-METHOXYETHOXY)ETHYL METHACRYLATE, AQUEOUS-SOLUTIONS, N-ISOPROPYLACRYLAMIDE, OLIGO(ETHYLENE GLYCOL) METHACRYLATE, POLYMERS, PROTEINS, SMART, SOLID TUMORS, STIMULI-RESPONSIVE POLYMERS, TEMPERATURE, TRANSFER RADICAL POLYMERIZATION}, isbn = {0024-9297}, url = {://000257665900045}, author = {Zou, Y. Q. and Brooks, D. E. and Kizhakkedathu, J. N.} }