@article {2698,
	title = {Barrier Capacity of Hydrophilic Polymer Brushes To Prevent Hydrophobic Interactions: Effect of Graft Density and Hydrophilicity},
	journal = {Macromolecules},
	volume = {42},
	number = {13},
	year = {2009},
	note = {ISI Document Delivery No.: 472NJTimes Cited: 7Cited Reference Count: 57Zou, Yuquan Rossi, Nicholas A. A. Kizhakkedathu, Jayachandran N. Brooks, Donald E.},
	month = {Jul},
	pages = {4817-4828},
	type = {Article},
	abstract = {The performance of biomaterials in contact with biological systems can be greatly affected by hydrophobic interactions at the interface between the biomaterial surface and surrounding biomolecules. Polymer brushes can function as a protective layer, preventing such interfacial hydrophobic interactions. In this paper, a systematic study of the barrier properties of a hydrophilic polymer brush is made by investigating the influence of graft density and its chemical nature (hydrophilicity/hydrophobicity) on hydrophobic interactions with the surface. To achieve this, it series of novel thermoresponsive poly-N-[(2,2-dimethyl-1,3-dioxolane)methyl]acrylamide (PDMDOMA) polymer brushes were grown from silicon wafers via surface-initiated atom transfer radical polymerization. Without changing graft density or degree of polymerization, the hydrophilicity of the PDMDOMA brushes was manipulated by partial or complete hydrolysis or the pendent dioxolane moieties. A lower critical solution temperature (LCST) was observed at 22-24 degrees C, below which the PDMDOMA brush was Found to be in a hydrated state (amphiphilic), while at temperatures above the LCST, the PDMDOMA brush formed a collapsed. more hydrophobic structure. A physical method was developed to analyze the ability of these brushes to act as a barrier against hydrophobic interactions based on AFM force-distance measurements. The adhesive forces between the Si3N4 tip and the silicon wafer surface upon (a) modification with ATRP initiator, (b) grafting of PDMDOMA brushes, and (c) partial and complete hydrolysis of PDMDOMA were investigated. Hydrophobic interactions decreased after each modification, while graft density and the degree of hydrolysis increased the barrier function of the surface layer. In particular, when graft density was above 0.22 chains/nm(2), the barrier capacity completely counteracted the hydrophobic interactions, as evidenced from the disappearance of the adhesive force in AFM measurements. Further Studies revealed that the barrier property its assessed by AFM correlated well with the wettability of the surfaces.},
	keywords = {ATOMIC-FORCE MICROSCOPY, BLOOD-PLASMA, CELL-ADHESION, CHAIN-LENGTH, HUMAN, MOLECULAR-WEIGHT, protein adsorption, SERUM-ALBUMIN, SINGLE-MOLECULE, SURFACE, TRANSFER RADICAL POLYMERIZATION},
	isbn = {0024-9297},
	url = {<Go to ISI>://000268138500067},
	author = {Zou, Y. Q. and Rossi, N. A. A. and Kizhakkedathu, J. N. and Brooks, D. E.}
}
@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 = {<Go to ISI>://000264145000068},
	author = {Kizhakkedathu, J. N. and Janzen, J. and Le, Y. and Kainthan, R. K. and Brooks, D. E.}
}
@article {2697,
	title = {Surface Modification of Polyvinyl Chloride Sheets via Growth of Hydrophilic Polymer Brushes},
	journal = {Macromolecules},
	volume = {42},
	number = {9},
	year = {2009},
	note = {ISI Document Delivery No.: 441PNTimes Cited: 7Cited Reference Count: 65Zou, Yuquan Kizhakkedathu, Jayachandran N. Brooks, Donald E.},
	month = {May},
	pages = {3258-3268},
	type = {Article},
	abstract = {Poly(N,N-dimethylacrylamide) (PDMA) brushes were successfully grown from polyvinyl chloride (uPVC) sheets via well-controlled surface-initiated atom transfer radical polymerization (SI-ATRP). An ATRP initiator containing a chloropropionate moiety was chemically tethered onto the surface of PVC via it novel wet chemical modification. Negatively charged sulfate groups were introduced to facilitate polymerization. By incorporating a chemically cleavable group into the initiator, molecular weight, polydispersity and graft density of a series of PDMA brushes synthesized on the flat surface were unambiguously characterized for the first time by gel permeation chromatography. ATR-FTIR, contact angle, SEM and AFM were used to characterize the PDMA grafted surfaces. Reaction conditions Such as monomer concentration, reaction time, copper(II) concentration and salt additives were varied to systematically investigate their effects on molecular weight and graft density of the PDMA grafted from PVC. Molecular weights of grafted PDMA brushes varied from ca. 20 000 to 2 170 000 Da, while craft density ranged from 0.08 to 1.13 chains/nm(2). Polydispersity of grafted PDMA brushes was controlled between 1.20 and 1.60 by Cu(II) complex addition. Kinetic studies revealed that the surface initiation was a slow process and graft density increased during the reaction. The brush uniformity increased with increasing reaction time. Reinitiation of the obtained PDMA brushes was demonstrated, suggesting that the polymerization is "living". The successful growth of a PDMA-b-poly(N-isopropylacrylamide) (PNIPAM) copolymer brush was verified by GPC and AFM.},
	keywords = {AQUEOUS ATRP, ATOMIC-FORCE MICROSCOPY, CARBON NANOTUBES, COPOLYMER BRUSHES, density, GLYCOL), GRAFT, PLASMA-PROTEIN ADSORPTION, POLY(ETHYLENE, SELF-ASSEMBLED MONOLAYERS, SERUM-ALBUMIN, TRANSFER RADICAL POLYMERIZATION},
	isbn = {0024-9297},
	url = {<Go to ISI>://000265781300007},
	author = {Zou, Y. Q. and Kizhakkedathu, J. N. 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 = {<Go to ISI>://000257665900045},
	author = {Zou, Y. Q. and Brooks, D. E. and Kizhakkedathu, J. N.}
}
@article {2226,
	title = {Synthesis of thermoresponsive mixed arm star polymers by combination of RAFT and ATRP from a multifunctional core and its self-assembly in water},
	journal = {Macromolecules},
	volume = {41},
	number = {12},
	year = {2008},
	note = {ISI Document Delivery No.: 314XSTimes Cited: 22Cited Reference Count: 80Ranganathan, Krishnan Deng, Rui Kainthan, Rajesh K. Wu, Chi Brooks, Donald E. Kizhakkedathu, Jayachandran N.},
	month = {Jun},
	pages = {4226-4234},
	type = {Article},
	abstract = {Mixed arm star copolymers of poly(N,N-dimethylacrylamide) (PDMA) and poly(N-isopropylacrylamide) (PNIPAm) were synthesized by a sequential reversible addition - fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) from a multi-initiator-functionalized hyperbranched polyglycerol (MI-HPG) core. The MI-HPG core was synthesized from an amine-functionalized polyglycerol, modified successively with 2-chloropropionamide groups (ATRP initiator) and 4,4{\textquoteright}-azobis(4-cyanovaleric acid) (azo initiator). N,N-Dimethylacrylamide was polymerized from MI-HPG core by the RAFT method using S,S{\textquoteright}-bis(alpha,alpha{\textquoteright}-dimethyla-alpha {\textquoteright}{\textquoteright}-acetic acid)trithiocarbonate as a chain transfer agent (CTA) in acetic acid/sodium acetate aqueous buffer solutions. The ratio of [CTA]/[azo initiator] was critical in controlling the molecular weight of the PDMA grafts from MI-HPG core (HPG-g-PDMA). Controlled synthesis of mixed arm star copolymers was achieved by cografting PNIPAm on to the HPG-g-PDMA macroinitiator by ATRP. The temperature-induced phase transition of aqueous solutions of hybrid HPG-g-PDMA/PNIPAm star copolymers was studied by H-1 NMR, UV-vis spectroscopy, and laser light scattering. Results show that the mixed arm star copolymers exist as either single molecules or small aggregates below the phase transition temperature (LCST) of PNIPAm in aqueous solutions. All the star copolymers formed intermolecular aggregates above the LCST of PNIPAm possibly due to the hydrophobic interaction between collapsed PNIPAM chains. These aggregates have micelle-like structure with PNIPAm core and PDMA corona. The formation of intermolecular aggregates and the stabilization of aggregates depend on the molecular weight of arms and composition of the star copolymer.},
	keywords = {AGGREGATION BEHAVIOR, AQUEOUS-SOLUTION PROPERTIES, DIBLOCK COPOLYMERS, FRAGMENTATION CHAIN TRANSFER, HYDROPHILIC BLOCK-COPOLYMERS, HYPERBRANCHED POLYGLYCEROL CORE, POLY(ETHYLENE OXIDE), TERTIARY AMINE METHACRYLATES, TO-GLOBULE TRANSITION, TRANSFER RADICAL POLYMERIZATION},
	isbn = {0024-9297},
	url = {<Go to ISI>://000256843100025},
	author = {Ranganathan, K. and Deng, R. and Kainthan, R. K. and Wu, C. and Brooks, D. E. and Kizhakkedathu, J. N.}
}
@article {909,
	title = {Synthesis and characterization of well-defined hydrophilic block copolymer brushes by aqueous ATRP},
	journal = {Polymer},
	volume = {45},
	number = {22},
	year = {2004},
	note = {ISI Document Delivery No.: 862NOTimes Cited: 27Cited Reference Count: 79},
	month = {Oct},
	pages = {7471-7489},
	type = {Article},
	abstract = {Homopolymer brushes of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA) and poly(N-isopropylacrylamide)(PNIPAM) grown on atom transfer radical polymerization (ATRP) initiator functionalized latex particles were used as macroinitiators for the synthesis of PDMA-b-PNIPAM/PMEA, PMEA-b-PDMA/PNIPAM and PNIPAM-b-PDMA block copolymer brushes by surface initiated aqueous ATRP. The grafted homopolymer and block copolymer brushes were analyzed for molecular weight, molecular weight distribution, chain grafting density, composition and hydrodynamic thickness (HT) using gel permeation chromatography-multi-angle laser light scattering, H-1 NMR, particle size analysis and atomic force microscopy (AFM) techniques. The measured graft molecular weight increased following the second ATRP reaction in all cases, indicating the second block had been added. Chain growth depended on the nature of the monomer used for block copolymerization and its concentration. Unimodal distribution of polymer chains in GPC with non-overlap of molar mass-elution volume curves implied an efficient block copolymerization. This was supported by the increase in HT measured by particle size analysis, equilibrium thickness observed by AFM and the composition of the block copolymer layer by H-1 NMR analysis, both in situ and on cleaved chains in solution. 1H NMR analysis of the grafted latex and cleaved polymers from the surface demonstrated that accurate determination of the copolymer composition by this method is possible without detaching polymer chains from surface. Block copolymer brushes obey the same power law dependence of HT on molecular weight as homopolymer brushes in good solvent conditions. The NIPAM-containing block copolymer brushes were sensitive to changes in the environment as shown by a decrease in HT with increase in the temperature of the medium. (C) 2004 Elsevier Ltd. All rights reserved.},
	keywords = {AMBIENT-TEMPERATURE, aqueous atom transfer radical polymerization, ATOMIC-FORCE MICROSCOPY, BRUSHES, CONTROLLED GROWTH, hydrophilic diblock copolymers, LIGHT-SCATTERING, METHYL-METHACRYLATE, N-DIMETHYLACRYLAMIDE), POLY(N, POLYELECTROLYTE BRUSHES, POLYMER BRUSHES, SELF-ASSEMBLED MONOLAYERS, SIZE-EXCLUSION CHROMATOGRAPHY, TRANSFER RADICAL POLYMERIZATION},
	isbn = {0032-3861},
	url = {<Go to ISI>://000224497900011},
	author = {Kizhakkedathu, J. N. and Kumar, K. R. and Goodman, D. and Brooks, D. E.}
}
@article {910,
	title = {Synthesis of well-defined environmentally responsive polymer brushes by aqueous ATRP},
	journal = {Macromolecules},
	volume = {37},
	number = {3},
	year = {2004},
	note = {ISI Document Delivery No.: 771TWTimes Cited: 102Cited Reference Count: 56},
	month = {Feb},
	pages = {734-743},
	type = {Article},
	abstract = {Functionalized anionic polystyrene latex particles with ATRP initiators were synthesized by surfactant-free shell-growth emulsion polymerization of styrene and 2-(2{\textquoteright}-chloropropionato)ethyl acrylate (HEA-Cl). N-Isopropylacrylamide (NIPAM) was polymerized from these particles by surface-initiated aqueous ATRP using PMDETA/CuCl and HMTETA/CuCl catalysts to synthesize poly(N-isopropylacrylamide) (PNIPAM) brushes. The grafted latexes were characterized for molecular weight of the PNIPAM chains, grafting density, and hydrodynamic thickness of the grafted polymer layer. Molecular weights of the grafted PNIPAM chains depended on the monomer concentration, concentration of copper(II) complex, and the presence of external initiator in the reaction medium. M-n of the grafted chains increases with increase in the monomer concentration and decreases with addition of copper(II) complex and external initiator. The HMTETA/CuCl catalyst produces higher molecular weight chains than PMDETA/CuCl. Molecular weights from similar to50 000 to 800 000 with low polydispersities, between 1.25 and 1.4, were achieved. The grafting density of PNIPAM on the surface increases with increasing monomer concentration and decreases with addition of copper(II) catalyst and external initiator. Block copolymerization of N,N-dimethylacrylamide from PNIPAM-grafted latex demonstrated that the chains are terminated with a chlorine atom, and the grafting reactions are taking place by the ATRP mechanism. The hydrodynamic thickness (HT) of the grafted PNIPAM layer scales as DP0.66 (where DP = degree of polymerization) at constant grafting density (chains/nm(2)). The HT values for PNIPAM brushes are sensitive to temperature and salt concentration. Since the transition from extended coil to collapsed structure occurs over a range of temperature and salt concentration, it follows a second-order transition, as predicted by theory. The thickness of the collapsed brush is sensitive to the type of stimulus used to induce the phase transition.},
	keywords = {GLOBULE TYPE TRANSITIONS, INTERFACES, N-DIMETHYLACRYLAMIDE) BRUSHES, PARTICLES, POLY(N, POLY(N-ISOPROPYLACRYLAMIDE), PROTEIN, SILICA, SURFACE-INITIATED POLYMERIZATIONS, TEMPERATURE, TRANSFER RADICAL POLYMERIZATION},
	isbn = {0024-9297},
	url = {<Go to ISI>://000188803000010},
	author = {Kizhakkedathu, J. N. and Norris-Jones, R. and Brooks, D. E.}
}
@article {653,
	title = {Synthesis of poly(N,N-dimethylacrylamide) brushes from charged polymeric surfaces by aqueous ATRP: Effect of surface initiator concentration},
	journal = {Macromolecules},
	volume = {36},
	number = {3},
	year = {2003},
	note = {ISI Document Delivery No.: 643NUTimes Cited: 49Cited Reference Count: 34},
	month = {Feb},
	pages = {591-598},
	type = {Article},
	abstract = {We have synthesized polystyrene shell latex (PSL) surfaces with different initiator concentrations by changing the feed ratio of styrene to 2-(methyl-2{\textquoteright}-chloropropionato)ethyl acrylate (HEACl) in a series of shell-growth copolymerization reactions. Surfaces were characterized by conductometric titration of saponified and nonsaponified functionalized PSL to give the surface charge and initiator concentrations accessible to aqueous reagents and by H-1 NMR methods. Poly(N,N-dimethylacrylamide) brushes were grafted from the functionalized surfaces by aqueous atom transfer radical polymerization and the dependence of molecular weight and chain density determined as a function of monomer concentration, ligand type, and surface initiator concentration by analyzing the chains cleaved from the PSL by saponification. M. varies linearly with monomer concentration for most systems, and grafting density is roughly independent of monomer concentration except at the highest initiator concentration. Very high molecular weights were obtained at low initiator concentration, up to M-n similar to 1.2 x 10(6) with M-w/M-n < 1.3; chain separations down to 1.1 mn and brush thicknesses to similar to800 nm were found. Grafting density varies as (initiator surface concentration)(2.6). The surface charge density also varies among the latexes synthesized and seems to play a role in this strong dependence on surface initiator concentration, perhaps by partially immobilizing the positively charged catalyst complex.},
	keywords = {ADSORPTION, SELF-ASSEMBLED MONOLAYERS, SUBSTRATE, TRANSFER RADICAL POLYMERIZATION},
	isbn = {0024-9297},
	url = {<Go to ISI>://000180868000015},
	author = {Kizhakkedathu, J. N. and Brooks, D. E.}
}
