Poly(2-oxazoline)s (POx) bottle-brush brushes have excellent biocompatible and lubricious properties, which are promising for the functionalization of surfaces for biomedical devices. Herein, a facile synthesis of POx is reported which is based bottle-brush brushes (BBBs) on solid substrates. Initially, backbone brushes of poly(2-isopropenyl-2-oxazoline) (PIPOx) were fabricated via surface initiated Cu0 plate-mediated controlled radical polymerization (SI-Cu0CRP). Poly(2-methyl-2-oxazoline) (PMeOx) side chains were subsequently grafted from the PIPOx backbone via living cationic ring opening polymerization (LCROP), which result in ≈100 % increase in brush thickness (from 58 to 110 nm). The resultant BBBs shows tunable thickness up to 300 nm and high grafting density (σ) with 0.42 chains nm−2. The synthetic procedure of POx BBBs can be further simplified by using SI-Cu0CRP with POx molecular brush as macromonomer (Mn=536 g mol−1, PDI=1.10), which results in BBBs surface up to 60 nm with well-defined molecular structure. Both procedures are significantly superior to the state-of-art approaches for the synthesis of POx BBBs, which are promising to design bio-functional surfaces. 相似文献
A universal and straightforward method for the preparation of polymer brushes via the formation of Si-C bond on silicon substrates through the UV-induced photopolymerization is demonstrated. 相似文献
Silica nanoparticles (NSiO2) are modified with mixed polymer brushes derived from a block copolymer precursor, poly(methyl methacrylate)-b-poly(glycidyl methacrylate)-b-poly(tert-butyl methacrylate) with short middle segment of PGMA, through one step ??grafting-onto?? approach. The block polymer precursors are prepared via reversible addition?Cfragmentation chain transfer-based polymerization of methyl methacrylate, glycidyl methacrylate, and tert-butyl methacrylate. The grafting is achieved by the reaction of epoxy group in short PGMA segment with silanol functionality of silica. After hydrolysis of poly(tert-butyl methacrylate) segment, amphiphilic NSiO2 with ??V-shaped?? polymer brushes possessing exact 1:1 molar ratio of different arms were prepared. The functionalized particles self-assemble at oil/water interfaces to form stable large droplets with average diameter ranging from 0.15?±?0.06 to 2.6?±?0.75?mm. The amphiphilicity of the particles can be finely tuned by changing the relative lengths of poly(methyl methacrylate) and poly(methacrylic acid) segments, resulting in different assembly behavior. The method may serve as a general way to control the surface property of the particles. 相似文献
ABSTRACTHerein, the polar anchoring energy coefficient (Aθ) of nematic liquid crystal (NLC) was examined for high-density polymer brushes via capacitance measurements. The Aθ is 10?4 J m?2 for the brushes of poly(methyl methacrylate), poly(ethyl methacrylate) and poly(styrene). The value decreases to 10?5 J m?2 for poly(n-butyl methacrylate) and poly(hexyl methacrylate) with lower glass transition temperatures. However, each polymer brush displays a constant Aθ value over a temperature range of ?15°C to 90°C, which is hardly affected by the graft density and brush thickness. At 25°C, Aθ is 10 times greater than the corresponding azimuthal anchoring energy coefficient (Aφ); therefore, NLCs on polymer brushes can be preferentially aligned along the in-plane component of the applied field. 相似文献
Acrylic polymers, including poly(methyl methacrylate), poly(2,2,2-trifluoroethyl methacrylate), poly( N,N'-dimethyaminoethyl methacrylate), and poly(2-hydroxyethyl methacrylate) were grafted from flat nickel and copper surfaces through surface-initiated atom transfer radical polymerization (ATRP). For the nickel system, there was a linear relationship between polymer layer thickness and monomer conversion or molecular weight of "free" polymers. The thickness of the polymer brush films was greater than 80 nm after 6 h of reaction time. The grafting density was estimated to be 0.40 chains/nm2. The "living" chain ends of grafted polymers were still active and initiated the growth of a second block of polymer. Block copolymer brushes with different block sequences were successfully prepared. The experimental surface chemical compositions as measured by X-ray photoelectron spectroscopy agreed very well with their theoretical values. Water contact angle measurements further confirmed the successful grafting of polymers from nickel and copper surfaces. The surface morphologies of all samples were studied by atomic force microscopy. This study provided a novel approach to prepare stable functional polymer coatings on reactive metal surfaces. 相似文献
Nanomechanical properties of end grafted polymer layers were studied by AFM based, colloidal probe compression measurements. Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) brush was grafted from planar Si surface and poly(methyl methacrylate) (PMAA) brush was grown on colloidal probe by surface initiated atom transfer radical polymerization. PMAA brush was further modified with adhesion promoting arginyl-glycyl-aspartic acid (RGD) peptide sequences. Force–distance curves were obtained for systems where the polymer brushes were probed on unmodified surfaces or face to each other. For each systems the grafting density of the polymer brush was determined applying a ‘box’ like polymer brush model based on the theory by de Gennes. ‘Average’ grafting density was calculated in cases when two polymer brushes face each other: RGD functionalized PMAA or PMAA against PSBMA. For our systems the values for the grafting density was between 0.04 and 0.11 nm?2. Furthermore the measured approach force–distance curves were fitted according to the Hertz model and the apparent Young’s modulus was determined for all measurements being in a range of around 250 kPa at physiological conditions. 相似文献
A facile and universal method is presented for the preparation of polymer brushes on amorphous TiO2 film. Homogeneous and stable poly(methyl methacrylate), polystyrene, poly(4‐vinylpyridine), and poly(N‐vinyl imidazole) (PNVI) brushes up to 550 nm are directly created onto TiO2 via UV‐induced photopolymerization of corresponding monomers. Kinetic studies reveal a linear increase in thickness with the polymerization time. Characterization of the resulting polymer brushes by FTIR spectroscopy, X‐ray photoelectron spectroscopy, contact angle, and atomic force microscopy (AFM) indicates an efficient UV‐grafting reaction. Finally, we have demonstrated the possibility in converting the PNVI brushes to poly(vinyl imidazolium bromide), i.e., poly(ionic liquid) brushes by polymer–analogous reactions.
The immobilization of enzymes on solid supports is an important challenge in biotechnology and biomedicine. In contrast to other methods, enzyme deposition in polymer brushes offers the benefit of high protein loading that preserves enzymatic activity in part due to the hydrated 3D environment that is available within the brush structure. The authors equipped planar and colloidal silica surfaces with poly(2-(diethylamino)ethyl methacrylate)-based brushes to immobilize Thermoplasma acidophilum histidine ammonia lyase, and analyzed the amount and activity of the immobilized enzyme. The poly(2-(diethylamino)ethyl methacrylate) brushes are attached to the solid silica supports either via a “grafting-to” or a “grafting-from” method. It is found that the grafting-from method results in higher amounts of deposited polymer and, consequently, higher amounts of Thermoplasma acidophilum histidine ammonia lyase. All polymer brush-modified surfaces show preserved catalytic activity of the deposited Thermoplasma acidophilum histidine ammonia lyase. However, immobilizing the enzyme in polymer brushes using the grafting-from method resulted in twice the enzymatic activity from the grafting-to approach, illustrating a successful enzyme deposition on a solid support. 相似文献
New soluble MoS2 nanosheets covalently functionalized with poly(N‐vinylcarbazole) (MoS2–PVK) were in situ synthesized for the first time. In contrast to MoS2 and MoS2/PVK blends, both the solution of MoS2–PVK in DMF and MoS2–PVK/poly(methyl methacrylate) (PMMA) film show superior nonlinear optical and optical limiting responses. The MoS2–PVK/PMMA film shows the largest nonlinear coefficients (βeff) of about 917 cm GW?1 at λ=532 nm (cf. 100.69 cm GW?1 for MoS2/PMMA and 125.12 cm GW?1 for MoS2/PVK/PMMA) and about 461 cm GW?1 at λ=1064 nm (cf. ?48.92 cm GW?1 for MoS2/PMMA and 147.56 cm GW?1 for MoS2/PVK/PMMA). A larger optical limiting effect, with thresholds of about 0.3 GW cm?2 at λ=532 nm and about 0.5 GW cm?2 at λ=1064 nm, was also achieved from the MoS2–PVK/PMMA film. These values are among the highest reported for MoS2‐based nonlinear optical materials. These results show that covalent functionalization of MoS2 with polymers is an effective way to improve nonlinear optical responses for efficient optical limiting devices. 相似文献
The in situ ATRP (atom transfer radical polymerization) "grafting from" approach was successfully applied to graft poly(methyl methacrylate) (PMMA) onto the convex surfaces of multiwalled carbon nanotubes (MWNT). The thickness of the coated polymer layers can be conveniently controlled by the feed ratio of MMA to preliminarily functionalized MWNT (MWNT-Br). The resulting MWNT-based polymer brushes were characterized and confirmed with FTIR, 1H NMR, SEM, TEM, and TGA. Moreover, the approach has been extended to the copolymerization system, affording novel hybrid core-shell nanoobjects with MWNT as the core and amphiphilic poly(methyl methacrylate)-block-poly(hydroxyethyl methacrylate) (PMMA-b-PHEMA) as the shell. The approach presented here may open an avenue for exploring and preparing novel carbon nanotubes-based nanomaterials and molecular devices with tailor-made structure, architecture, and properties. 相似文献
For designing the responsive polymer brushes, and tuning the local and chemical surface responses to the external stimuli, the epitaxial single crystals were patterned by combination of bared surfaces of poly(ethylene glycol) (PEG) substrate, polymer homo-brushes constructed from poly(ethylene glycol)-b-polystyrene (PEG-b-PS) as well as poly(ethylene glycol)-b-poly(methyl methacrylate) (PEG-b-PMMA), and PEG-b-PS/PEG-b-PMMA mixed-brush channels. To achieve this target, various single crystals and epitaxial structures grown from dilute solutions through self-seeding approach were utilized as seeds to fabricate the next channels. The characteristics and morphologies of different channels were detectable by atomic force microscopy (AFM). The influence of chemical (solvent quality and interaction of substrate with different brushes) and physical (presence of brushes from another type in their vicinity) environments on crystallization was studied. Due to the effect of chemical environment, the PS brushes hampered the growth of PEG crystals at MnPS?=?10,000 g/mol. However, the PMMA brushes allowed PEG crystals to grow completely at MnPMMA =13,100 g/mol, and indicated their hindrance at higher molecular weights (here, MnPMMA?=?17,100 g/mol). It was feasible to neutralize the mentioned hindrance through fabricating the channels with brushes having the highest hindrance (MnPS?=?14,800 g/mol and MnPMMA?=?17,100 g/mol), and altering the physical environment from homo- to mixed-brush morphology. The characteristics (thickness, tethering density, and domain size) of developed channels from a certain material, in all arrangements and in various channels were in good agreement with those of corresponding non-epitaxial single crystals grown under the same conditions. 相似文献
This report describes the remarkably rapid synthesis of polymer brushes under mild conditions (50 degrees C) using surface-initiated polymerization. The highly active atom transfer radical polymerization catalyst Cu(I)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane allows synthesis of 100 nm thick poly(tert-butyl acrylate) brushes from initiator-modified Au surfaces in just 5 min. Using the same catalyst, polymerization of 2-hydroxyethyl methacrylate and methyl methacrylate yielded 100 nm thick films in 10 and 60 min, respectively. Such growth rates are an order of magnitude greater than those for traditional free-radical polymerizations initiated from surfaces. These polymerizations also retain some features of controlled radical polymerizations, such as the ability to form block copolymer brushes. 相似文献
The new oxazoline-containing monomers, 4-acrylyloxymethyl-2,4-dimethyl-2-oxazoline (AOMO), 4-methacrylyloxymethyl-2,4-dimethyl-2-oxazoline (MAOMO), 4-methacrylyloxymethyl-2-phenyl-4-methyl-2-oxazoline (PMAOMO), and the previously known monomer, 2-isopropenyl-4,4-dimethyl-2-oxazoline (IPRO), were synthesized for addition polymerization studies. The monomers were homopolymerized in benzene using a free radical initiator and in aqueous media using emulsion techniques. Molecular weights of 8,000–15,000 (M?w) were obtained for the homopolymers. Copolymerization studies were carried out with AOMO, MAOMO, and IPRO as M1, and methyl methacrylate (MMA), methyl acrylate (MA), styrene (STY), acrylonitrile (AN), and vinyl acetate (VA) as M2 for each case of M1. Relative reactivity ratios for the fifteen copolymers and Q and e values for the three oxazoline monomers were determined. The r1 values for AOMO and MAOMO copolymerizations indicated a lower value of k11 than expected, presumably because of steric effects. The r1 values in the IPRO copolymerizations were somewhat larger than expected. It was proposed that significant electron donation to the radical center of IPRO·by resonance effects occured. 相似文献