The site‐specific attachment of nanoparticles is of interest for biomaterials or biosensor applications. Polymer brushes can be used to regulate this adsorption, so the conditions for selective adsorption of phosphonate‐functionalized nanoparticles onto micropatterned polymer brushes with different functional groups are optimized. By choosing the strong polyelectrolytes poly(3‐sulfopropyl methacrylate), poly(sulfobetaine methacrylate), and poly[2‐(methacryloyloxy)ethyl trimethylammonium chloride], it is possible to direct the adsorption of nanoparticles to specific regions of the patterned substrates. A pH‐dependent adsorption can be achieved by using the polycarboxylate brush poly(methacrylic acid) (PMAA) as substrate coating. On PMAA brushes, the nanoparticles switch from attachment to the brush regions to attachment to the grooves of a patterned substrate on changing the pH from 3 to 7. In this manner, patterned substrates are realized that assemble nanoparticles in pattern grooves, in polymer brush areas, or substrates that resist the deposition of the nanoparticles. The nanoparticle deposition can be directed in a pH‐dependent manner on a weak polyelectrolyte, or is solely charge‐dependent on strong polyelectrolytes. These results are correlated with surface potential measurements and show that an optical trap is a versatile method to directly probe interactions between nanoparticles and polymer brushes. A model for these interactions is proposed based on the optical trap measurements. 相似文献
High‐density polymer brushes on substrates exhibit unique properties and functions stemming from the extended conformations due to the surface constraint. To date, such chain organizations have been mostly attained by synthetic strategies of surface‐initiated living polymerization. We show herein a new method to prepare a high‐density polymer brush architecture using surface segregation and self‐assembly of diblock copolymers containing a side‐chain liquid‐crystalline polymer (SCLCP). The surface segregation is attained from a film of an amorphous base polymer (polystyrene, PS) containing a minor amount of a SCLCP‐PS diblock copolymer upon annealing above the glass‐transition temperature. The polystyrene portion of the diblock copolymer can work as a laterally mobile anchor for the favorable self‐assembly on the polystyrene base film. 相似文献
Hydrophilic polymer brushes grown via surface‐initiated polymerization from silicon oxide surfaces can detach or degraft in aqueous media. Degrafting of these chain end‐tethered polymers is believed to involve hydrolysis of bonds at the polymer–substrate interface. Degrafting so far has not been reported for hydrophobic polymer brushes in non‐aqueous media. This study has investigated the degrafting and swelling properties of poly(tert‐butyl methacrylate) (PtBMA) brushes in different water‐miscible, organic solvents, viz. DMF, acetone and THF. In the presence of a sufficient quantity of water in the organic solvent, degrafting was also observed for PtBMA brushes. More importantly, however, the rate of degrafting depended on the nature of the organic solvent and the apparent initial rate constant of the degrafting reaction was found to correlate with the swelling ratio of the polymer brush in the different solvents. This correlation is first, direct evidence in support of the hypothesis that degrafting is facilitated by a tension that acts on the bond(s) that tether the polymer chains to the surface and which is amplified upon swelling of the polymer brush. 相似文献
Summary: The communication provides a novel and alternative route to generate chemically tethered binary polymer‐brush pattern through two‐step surface‐initiated atomic‐transfer radical polymerization (SI‐ATRP). Polymer brush‐1 was prepared by SI‐ATRP, passivated by a reaction with NaN3, and etched with UV irradiation through a transmission electron microscopy grid to create exposed sites for the subsequently attached initiator on which polymer brush‐2 was grown.
Schematic representation of the resultant binary polymer brush patterns. 相似文献
Immobilization of enzymes onto carriers is a rapidly growing research area aimed at increasing the stability, reusability and enzymolysis efficiency of free enzymes. In this work, the role of phase-separation and a pH-responsive “hairy” brush, which greatly affected the topography of porous polymer membrane enzyme reactors (PMER), was explored. The porous polymer membrane was fabricated by phase-separation of poly(styrene-co-maleic anhydride-acrylic acid) and poly(styrene-ethylene glycol). Notably, the topography and pores size of the PMER could be controlled by phase-separation and a pH-responsive “hairy” brush. For evaluating the enzymolysis efficiency of d-amino acid oxidase (DAAO) immobilized carrier (DAAO@PMER), a chiral ligand exchange capillary electrophoresis method was developed with d-methionine as the substrate. The DAAO@PMER showed good reusability and stability after five continuous runs. Notably, comparing with free DAAO in solution, the DAAO@PMER exhibited a 17.7-folds increase in catalytic velocity, which was attributed to its tailorable topography and pH-responsive property. The poly(acrylic acid) moiety of poly(styrene-co-maleic anhydride-acrylic acid) as the pH-responsive “hairy” brush generated topography changing domains upon adjusting the buffer pH, which enable the enzymolysis efficiency of DAAO@PMER to be tuned based upon the well-defined architectures of the PMER. This approach demonstrated that the topographical changes formed by phase-separation and the pH-responsive “hairy” brush indeed made the proposed porous polymer membrane as suitable supports for enzyme immobilization and fitting for enzymolysis applications, achieving high catalytic performance. 相似文献
Polymer brush films with chemical functionality to attach to site specific substrate areas are introduced for area selective deposition (ASD) application. It is demonstrated that polymer brushes with chemically defined end sites can be selectively bound to copper‐specific regions of patterned copper/silica (Cu/SiO2) substrates. The process described overcomes various limitations of currently used technology including cost, complexity, and throughput, with potential implications for future electronic devices and nanomanufacturing. A comparative study of amine‐terminated polystyrene and amine‐terminated poly‐2‐vinyl pyridine polymer brushes (i.e., PS‐NH2 and P2VP‐NH2) with similar molecular weights display contrasting behavior on patterned Cu/SiO2 line features. Further, a thiol terminated poly‐2‐vinyl pyridine polymer brush (i.e., P2VP‐SH) is investigated as a direct spin‐on process to fabricate a metal oxide layer atop Cu areas only. The results presented here detail a novel methodology and open a new exciting process for ASD practices that can facilitate the precise deposition of dense metal, semiconductor, or dielectric films. We also discuss the applicability of polymer brushes to ASD uses going forward. 相似文献
A polymer brush containing a diethylamino group as an anion-exchange group was appended onto a polymer substrate by radiation-induced graft polymerization and subsequent chemical modifications. Bovine serum albumin as a chiral ligand for L-tryptophan was bound to the polymer brush at a density ranging from 17 to 150 g BSA/l. For comparison, BSA was adsorbed onto the gel network containing a diethylaminoethyl group. The molar binding ratio of L-tryptophan to BSA on the polymer brush was 1.7-fold higher than that to BSA on the gel network. 相似文献
Structural properties of polymer brushes tethered on a periodically nanopatterned substrate are investigated by computer simulations. The substrate consists of an alternating succession of two different types of equal-width parallel stripes, and the polymers are end-tethered selectively on every second stripe. Three distinct morphologies of the nanopatterned brush have been identified, and their range of stability has been determined in terms of a single universal parameter that combines the grafting density, the polymer length, and the stripe width. We propose scaling relations for the average brush height and for the architectural properties of the outer surface of the nanopatterned brush under good solvent conditions. Our analysis provides guidelines for fabricating well-defined and tunable nanopatterned polymeric films. 相似文献
Summary: The influence of a lateral force (or lateral shear) acting on chains in a polymer brush is investigated theoretically. Brushes consisting of chains with temperature dependent anisotropic interactions between monomers (main‐chain mesogenic groups) are considered. It is shown that a lateral force applied to polymer brush induces its compression. In contrast to a conventional brush, the compression of brush, capable of forming a liquid crystalline (LC) state, can be caused by comparatively small shear forces. Moreover, such shear forces can induce a phase transition of a brush into the tilted LC state with a several‐fold decrease in brush thickness. These results allow us to predict a possibility to observe a decrease in brush thickness in a real experiment with reasonably values of shear rate.
Model of a chain in a polymer brush under an influence of lateral force p. 相似文献
The era of poly(ethylene glycol) (PEG) brushes as a universal panacea for preventing non‐specific protein adsorption and providing lubrication to surfaces is coming to an end. In the functionalization of medical devices and implants, in addition to preventing non‐specific protein adsorption and cell adhesion, polymer‐brush formulations are often required to generate highly lubricious films. Poly(2‐alkyl‐2‐oxazoline) (PAOXA) brushes meet these requirements, and depending on their side‐group composition, they can form films that match, and in some cases surpass, the bioinert and lubricious properties of PEG analogues. Poly(2‐methyl‐2‐oxazine) (PMOZI) provides an additional enhancement of brush hydration and main‐chain flexibility, leading to complete bioinertness and a further reduction in friction. These data redefine the combination of structural parameters necessary to design polymer‐brush‐based biointerfaces, identifying a novel, superior polymer formulation. 相似文献
A dithiolated random copolymer with pendent phenylboronic acid residues (Cys-Poly(3-acrylamidophenylboronic acid-co-2-dimethylaminopropyl methacrylamide), Cys-Poly(APBA-co-DMAPMA)) obtained by photo-iniferter method was accumulated as a polymer brush on a cap-shaped gold particles deposited on a vacuum-evaporated gold film, and the usefulness of the polymer brush as a sensing element for glycoprotein, ovalbumin (OVA), was examined by using UV-vis spectroscopy with a help of surface plasmon resonance. A similar system was constructed with a dithiolated mannose-carrying polymer, dithiolated-poly(2-methacryloyloxyethyl-D-mannopyranoside) (DT-PMEMan), prepared by the atom transfer radical polymerization (ATRP). The brush composed of this polymer was examined as a sensing element for lectin, concanavalin A (Con A). The sensor cells modified with Cys-Poly(APBA-co-DMAPMA) and DT-PMEMan showed a concentration-dependent binding of OVA and Con A, respectively, with a comparable detection limit to those with a monolayer of polymer brush-coated gold particle deposited on a glass substrate. Using this system, it can be expected to open a new perspective to various functional polymer brushes fixed to the cap-shaped gold particle on a solid substrate. 相似文献
An analogue of the Alexander‐DeGennes box model is used for theoretical investigation of polymer brushes in a mixture of two solvents. The basic solvent A and the admixture B are assumed to be highly incompatible (Flory‐Huggins parameter χAB = 3.5). Thermodynamics of a polymer in the solvents A and B are described by parameters χB < χA ≤ 1/2. The equilibrium behavior of a brush is investigated in dependence on solvent composition, grafting density, polymer‐solvents and solvent‐solvent interactions. The possibility of a phase transition related with a strong preferential solvation of a brush by a minor solvent component with higher affinity to polymer is shown and examined. Microphase segregation inside a brush is also demonstrated despite overestimating of the brush homogeneity given by the box model. A further simplification of the model permits to obtain scaling formulas and to investigate main regularities in the brush behavior. This offers a clear physical picture of the phase segregation inside a brush in correlation with the phase state of a bulk solvent. 相似文献