Photocrosslinkable Copolymers Research Articles

Single-Component Hydrophilic Terpolymer Thin Film Systems for Imparting Surface Chemical Versatility on Various Substrates.

We demonstrate a single-component hydrophilic photocrosslinkable copolymer system that incorporates all critical functionalities into one chain. This design allows for the creation of uniform functional organic coatings on a variety of substrates. The copolymers were composed of a poly(ethylene oxide)-containing monomer, a monomer that can release a primary amine upon UV light, and a monomer with reactive epoxide or cyclic dithiocarbonate with a primary amine. These copolymers are easily incorporated into the solution-casting process using polar solvents. Furthermore, the resulting coating can be readily stabilized through UV light-induced crosslinking, providing an advantage for controlling the surface properties of various substrates. The photocrosslinking capability further enables us to photolithographically define stable polymer domains in a desirable region. The resulting copolymer coatings were chemically versatile in immobilizing complex molecules by (i) post-crosslinking functionalization with the reactive groups on the surface and (ii) the formation of a composite coating by mixing varying amounts of a protein of interest, i.e., fish skin gelatin, which can form a uniform dual crosslinked network. The number of functionalization sites in a thin film could be controlled by tuning the composition of the copolymers. In photocrosslinking and subsequent functionalizations, we assessed the reactivity of the epoxide and cyclic dithiocarbonate with the generated primary amine. Moreover, the orthogonality of the possible reactions of the presented reactive functionalities in the crosslinked thin films with complex molecules is assessed. The resulting copolymer coatings were further utilized to define a hydrophobic surface or an active surface for the adhesion of biological objects.

Preparation of photo-crosslinkable acrylic copolymer and its debonding property on silicon wafer

As silicon wafers become thinner and easier to warp, it is important to improve production efficiency of dies. In the wafer grinding and dicing process, photo-crosslinkable pressure sensitive adhesive (PSA) tapes are applied to fix the silicon wafer and greatly increase die yield. The PSA tapes must be peeled easily without any residues after UV light irradiation. Herein, a hydroxyl group containing copolymer was first synthesized from 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid and hydroxyethyl acrylate monomers via free radical polymerization, followed by the introduction of methacrylate groups through the addition reaction of 2-isocyanatoethyl methacrylate with hydroxyl groups on side chain of copolymers. The photo-crosslinkable adhesive was then prepared by the mixing the copolymers with photoinitiator and aziridine crosslinker. Glass transition temperature (Tg) and storage modulus of the photo-crosslinked adhesives increased with UV irradiation time, which benefited the picking-up process. A digital microscope was used to observe the surface morphology of the debonded silicon wafers and excellent debonding effect occurred after 40 s UV irradiation.

In Situ Surface Modification of Microfluidic Blood-Brain-Barriers for Improved Screening of Small Molecules and Nanoparticles.

Here, we have developed and evaluated a microfluidic-based human blood-brain-barrier (μBBB) platform that models and predicts brain tissue uptake of small molecule drugs and nanoparticles (NPs) targeting the central nervous system. By using a photocrosslinkable copolymer that was prepared from monomers containing benzophenone and N-hydroxysuccinimide ester functional groups, we were able to evenly coat and functionalize μBBB chip channels in situ, providing a covalently attached homogenous layer of extracellular matrix proteins. This novel approach allowed the coculture of human endothelial cells, pericytes, and astrocytes and resulted in the formation of a mimic of cerebral endothelium expressing tight junction markers and efflux proteins, resembling the native BBB. The permeability coefficients of a number of compounds, including caffeine, nitrofurantoin, dextran, sucrose, glucose, and alanine, were measured on our μBBB platform and were found to agree with reported values. In addition, we successfully visualized the receptor-mediated uptake and transcytosis of transferrin-functionalized NPs. The BBB-penetrating NPs were able to target glioma cells cultured in 3D in the brain compartment of our μBBB. In conclusion, our μBBB was able to accurately predict the BBB permeability of both small molecule pharmaceuticals and nanovectors and allowed time-resolved visualization of transcytosis. Our versatile chip design accommodates different brain disease models and is expected to be exploited in further BBB studies, aiming at replacing animal experiments.

Synthesis of Photocrosslinkable Copolymers of Cinnamoyl Group-modified Methacrylate and 2-Hydroxyethyl Methacrylate, and Fibroblast Cell Growth on Their Thin Films

Synthesis of Photocrosslinkable Copolymers of Cinnamoyl Group-modified Methacrylate and 2-Hydroxyethyl Methacrylate, and Fibroblast Cell Growth on Their Thin Films

Photo-crosslinkable comb-type copolymers bearing a benzophenone moiety for the enhanced swelling kinetics of hydrogels

The fast responding 3D hydrogel object was fabricated using developed photo-crosslinkable copolymers bearing grafted PNIPAm and a benzophenone moiety.

Synthesis of Polythiophene with a Photo-Crosslinkable Side Chain

We have synthesized a photo-crosslinkable polythiophene copolymer functionalized with a cinnamate moiety to improve the stability of organic photovoltaic (OPV) cells. The active layer of OPV cells is generally bulk heterojunction (BHJ) that consists of two or more organic semiconductors. When BHJ forms a micro-phase-separated structure with a blend of two organic materials, its structure inclines to change into a macro-phase-separated one after some time. To stabilize the BHJ morphology, we used a crosslinkable polymer containing a cinnamate moiety. The copolymer film became insoluble after UV irradiation because of [2+2] dimerization of the cinnamate groups.

Photoageing of cardanol: characterization, circumvention by side chain methoxylation and application for photocrosslinkable polymers

Photoageing of cardanol and its limitation by methoxylation of the side chain to produce photocrosslinkable copolymers of tunable reactivity.

Programming reversibly self-folding origami with micropatterned photo-crosslinkable polymer trilayers.

Self-folding microscale origami patterns are demonstrated in polymer films with control over mountain/valley assignments and fold angles using trilayers of photo-crosslinkable copolymers with a temperature-sensitive hydrogel as the middle layer. The characteristic size scale of the folds W = 30 μm and figure of merit A/ W (2) ≈ 5000, demonstrated here represent substantial advances in the fabrication of self-folding origami.

Molecular Reorientation Behavior of Photocrosslinkable Liquid Crystalline Copolymer Films Composed of 4-(4-Methoxycinnamoyloxy)biphenyl and Phenylester Side Groups

The cooperative molecular reorientation in methacrylate copolymer films comprising photoreactive 4-(4-methoxycinnamoyloxy)biphenyl and phenylester in their side chains was investigated by irradiation with linearly polarized ultraviolet light and subsequent annealing. Both cinnamate and phenylester side groups were miscible in the copolymer composition, and axis-selective photoreaction of the cinnamate groups was observed. Thermally enhanced cooperative in-plane orientation of both side groups was obtained when the irradiated films were annealed in the liquid crystalline temperature range of the copolymers.

Edge-defined metric buckling of temperature-responsive hydrogel ribbons and rings

We report the temperature-responsive buckling of ribbon-like hydrogel thin films based on photo-crosslinkable copolymers of poly(N-isopropyl acrylamide) (PNIPAM) with pendent benzophenone units. Due to the finite resolution of the photo-lithographic patterning method—here dominated by the convergence of light from the illumination source—nominally homogeneous layers are always surrounded by a more highly swelling border with a lateral size scale similar to the film thickness. As one of the in-plane dimensions of the gel sheet is reduced to only several times its thickness, this edge effect serves as a sufficiently large imperfection to drive buckling of the otherwise metrically flat ribbon. Due to the symmetric geometry, the resulting geometry has essentially constant curvature of the mid-line of the ribbon, with a radius of curvature defined by its thickness and width. In this manner, we prepare thermally responsive overcurved rings that buckle into more highly coiled configurations as they swell, due to the mismatch in metric curvature relative to the geometric shape of the object. We consider the conditions for unfrustrated coiling of both circular and polygonal rings in terms of the number of self-crossings made upon wrapping the surface of a sphere, and demonstrate the fabrication of ‘self-cinching unknots’, i.e. coiled ribbons that can fasten themselves onto other objects upon deswelling, due to topological constraints.

A novel electrochemical sensor for paracetamol based on molecularly imprinted polymeric micelles

A novel molecular imprinted polymeric (MIP) micelle was prepared via macromolecule self-assembly of an amphiphilic photo-crosslinkable copolymer in combination with a molecular imprinting technique using paracetamol as the template molecule, and applied as a molecular recognition element to construct paracetamol (PCM) electrochemical sensor. The template molecules (PCM) were imbedded in the copolymer micelle during the self-assembly micellization of amphiphilic copolymers through the interactions between PCM and copolymer chain. A robust MIP film was formed in situ on the electrode surface by electrodeposition of the MIP micelles and subsequent photo-crosslinking, leading to successful construction of a MIP sensor. Using differential pulse stripping voltammetry (DPSV), selective detection of PCM in a linear concentration range of 1μM–4mM was obtained, revealing wider linear response and higher upper detection limit of detection compared to previously reported PCM electrochemical sensors, which was attributed to numerous effective recognition sites among the polymer matrix due to the large specific surface area of MIP micelles. In addition, this MIP sensor showed excellent selectivity to PCM, and the interferences from structurely similar analogs were effectively avoided. Excellent stability and repeatability has also been exhibited. Finally, it was successfully applied to detect PCM in real samples with good recoveries. Together, these results indicate that our MIP sensor is a promising platform for accurate and reproducible detection of PCM.

Paracetamol Sensor Based on Molecular Imprinting by Photosensitive Polymers

AbstractA voltammetric paracetamol sensor based on molecularly imprinted polymeric (MIP) micelles was prepared by direct electrodeposition. The MIP micelles were prepared via macromolecule self‐assembly of an amphiphilic photocrosslinkable copolymer using paracetamol as the template molecule. The resultant molecularly imprinted polymeric micelles swelled with increasing pH, and the disassociation of the micelles occurred at pH above approximately 7.4. A robust MIP film with good solvent resistance was formed on the electrode surface by anodic electrodeposition of the MIP micelles and subsequent photocrosslinking, resulting in the fabrication of a MIP electrochemical sensor for detecting paracetamol. The resultant sensor showed good response and selectivity towards paracetamol. In addition, a wide linear range from 0.01 mmol/L to 8 mmol/L and a low detection limit of 1×10−6 mol/L for paracetamol detection was demonstrated based on this sensor. The MIP sensor also showed good stability and reversibility which was applied to determine paracetamol commercial tablets.

Research on Amphiphilic Copolymer MIP Micelles Electrochemical Sensor

Novel molecularly imprinted polymeric (MIP) micelles were prepared via macromolecule self-assembly of a photo-crosslinkable copolymer, combined with molecular imprinting technique using 4-acetaminophenol as the template molecule. First, an acrylic copolymer poly(DMA-co-HEA-co-EHA-co-St) was synthesized via free radical polymerization using (dimethylamino)ethylmethacrylate (DMA), 2-hydroxy ethylacrylate (HEA), 2-ethylhexyl acrylate (EHA) and styrene (St). Further post functionalization introduced a cross-linkable acrylate side groups into the polymer to form the photo-crosslinkable copolymer using isophorone diisocyanate (IPDI) as bridges. The photo-crosslinkable copolymer and 4-acetaminophenol were dissolved to give copolymer mixed solution. Water as a non-solvent, was added to the mixed solu- tion to induce the self-assembly micellization of the photo-crosslinkable copolymer, during which the template molecules (4-acetaminophenol) was entrapped in the micelles through the interactions between 4-acetaminophenol and the copolymer chain. The properties and morphology of MIP micelles were characterized by dynamic light scattering (DLS), zeta potential and transmission electron microscope (TEM). DLS results showed that the average hydrodynamic diameter was about 70 nm, which was supported by the result from the TEM measurements. The MIP micelle solution prepared was used as a bath solu- tion for electrodeposition. A MIP film was formed in situ on the electrode surface by electrodeposition of the MIP micelles and then crosslinked by UV radiation to lock the structure and improve the stability of the film. Finally the template mole- cules were removed from the film by extraction, leading to 4-acetaminophenol imprinted electrode. The electrochemical per- formance of the MIP electrode was evaluated by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The resulting MIP sensor showed good response and selectivity towards 4-acetaminophenol. In addition, this MIP sensor showed excellent selectivity to 4-acetaminophenol, and the interferences from structurely similar analogues were ef- fectively avoided. The linear range was from 1×10

Photoreactive oligoethylene glycol polymers – versatile compounds for surface modification by thin hydrogel films

Solid surfaces are modified using photo-crosslinkable copolymers based on oligo(ethylene glycol) methacrylate (OEGMA) bearing 2-(4-benzoylphenoxy)ethyl methacrylate (BPEM) as a photosensitive crosslinking unit. Thin films of about 100 nm are formed by spin-coating these a priori highly biocompatible copolymers onto silicon substrates. Subsequent UV-irradiation assures immobilization and crosslinking of the hydrogel films. Their stability is controlled by the number of crosslinker units per chain and the molar mass of the copolymers. The swelling of the hydrogel layers, as investigated by ellipsometry, can be tuned by the crosslinker content in the copolymer. If films are built from the ternary copolymers of OEGMA, BPEM and 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA), the hydrogel films exhibit a swelling/deswelling transition of the lower critical solution temperature (LCST) type. The observed thermally induced hydrogel collapse is fully reversible and the onset temperature of the transition can be tuned at will by the copolymer composition. Different from analogously prepared thermo-responsive hydrogel films of photocrosslinked poly(N-isopropylacrylamide), the swelling–deswelling transition occurs more gradually, but shows no hysteresis.

Glucose sensors based on electrodeposition of molecularly imprinted polymeric micelles: A novel strategy for MIP sensors

A voltammetric glucose sensor was prepared from novel molecularly imprinted polymeric micelles (MIPMs) through direct electrodeposition. The MIPMs, which were photo-crosslinkable and nano-scaled with high specific surface area, were prepared via macromolecule self-assembly of an amphiphilic photo-crosslinkable copolymer, combined with a molecular imprinting technique using glucose as the template molecule. A MIP film was formed in situ on the electrode surface by electrodeposition of the MIPMs, while photo-crosslinking led to a robust film which showed good solvent resistant to dissolution. With these features, the resulting sensor showed good response and selectivity towards glucose. In particular, the linear response of this glucose sensor ranged from 0.2 mM to 8 mM and its comparatively higher detection limit, about 10 mM, indicated numerous effective recognition sites among the polymer matrix due to the large specific surface area of MIPM. In addition, this MIP sensor also showed good stability and reversibility. The contribution of this work lies in not only the invention of a new type of glucose MIP sensor with good performance, but also the creation of a novel strategy to develop advanced MIP sensors for a wide range of templates in viewing of the versatility of the amphiphilic copolymers and the ease of control and applicability of the electrodeposition process.

알루미나 기재에 부착된 습도센서용 자기 가교형 감습성 전해질 고분자의 내수성

New cinnamate group-containing copolymers for a self-curable, humidity-sensitive polyelectrolyte and polymeric anchoring agents were prepared by copolymerization of [2-[(methacryloyloxy) ethyl]dimethyl]propyl ammonium bromide(MEPAB), methyl methacrylate(MMA), 3-(trimethoxysilyl) propyl methacrylate(TMSPM) and 2-(cinnamoyloxy)ethyl methacrylate(CEMA). Photocrosslinkable copolymer composed of MEPAB/MMA/TMSPM/CEMA＝70/20/0/10 were used for humidity-sensitive membrane, and those of 50/0/20/30 and 0/0/50/50 were used for polymeric anchoring agents. 3- (Triethoxysilyl)propyl cinnamate(TESPC) was also used as a surface-pretreating agent for the comparison of capability of attachment of polyelectrolyte to the electrode surface with polymeric photocurable silanecoupling agents. Pretreatment of the electrode substrate with anchoring agents was performed to form a cinnamate thin film on the electrode through covalent bonds. When the sensors were irradiated with UV light, the anchoring of a polyelectrolyte into the substrate was carried out via the [2+2] cycloaddition. The resulting sensors using polymeric anchoring agents and TESPC showed water durability with increase of resistance by 60~85%, which is corresponding to the reduction of 2.25~3.15%RH, after soaking in water for 24 h. They showed good hysteresis (-0.2%RH), response time (90 sec) and long-term stability at high temperature and humidity.

Photolithography of a photocrosslinkable copolymer prepared from a 2-styrylpyridine group-containing maleimide and N-dodecyl maleimide

Photolithography of a photocrosslinkable copolymer prepared from a 2-styrylpyridine group-containing maleimide and N-dodecyl maleimide

Photopatternable substrate‐independent poly(glycidyl methacrylate‐ran‐2‐(acryloyloxy) ethyl 2‐methylacrylate) polymer films for immobilization of biomolecules

AbstractWe report the synthesis and characterization of a photocrosslinkable copolymer containing reactive epoxy groups for binding biomolecules. The epoxide‐containing copolymer poly(glycidyl methacrylate‐ran‐2‐(acryloyloxy) ethyl 2‐methylacrylate) offers distinct advantages such as ease of application to various substrates, enhanced stability of the bound oligonucleotide, low autofluorescence, and the ability to be photopatterned allowing localization of the linkers. The copolymer uses pendant acryloyl groups to control the crosslinking without sacrificing the epoxide groups. The films were characterized using ellipsometry, atomic force microscopy, and fluorescence microscopy. The films on glass, silicon wafer, and stainless steel showed no appreciable degradation in water, tetrahydrofuran, and acetone for ∼4 months. The surface topography for a given thickness of crosslinked film was dictated by the deposition conditions. A 16mer oligonucleotide was immobilized on the thin films. A linear relationship between the film thickness and amount of oligonucleotide immobilized was observed with a maximum signal‐to‐background ratio (S/B) of 225 for a 60‐nm‐thick film, a value 50% higher than the S/B for an epoxide monolayer. The crosslinked films maintained a high fluorescence signal following long aqueous washing which is appealing for biological microarrays, immobilizing proteins, and study of slow differentiating cells where stability of the scaffold is relevant. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5826–5838, 2008

Polarized-Light-Induced Enhancement of the Electro-Optic Properties in a Photoreactive Maleimide Copolymer

A photocrosslinkable maleimide copolymer has been synthesized using a tricyanopyrrolidene (TCP)-based chromophore. The 2-(3-Cyano-4-(2-{4-[hexyl-(6-hydroxy-hexyl)-amino]-phenyl}vinyl)-5-oxo-1-{4-[4-(3-oxo-3-phenyl-propenyl)-phenoxy]-butyl}-1,5-dihydro-pyrrol-2-ylidene)-malononitrile chromophore (DHATCP-CH) exhibits nonlinear optical activity and contains a chalcone moiety that is highly sensitive to UV light for crosslink formation. The maleimide monomer was also functionalized with chalcone moieties. The electro-optic signal can be varied under irradiation with linearly polarized light. The enhancement of the electro-optic effect in the copolymer is attributed to an angular selective photocrosslink formation upon illumination with p-polarized UV light. A possible mechanism that can explain this phenomenon is presented.

Studies on photocrosslinkable copolymers of 4-methacryloyloxyphenyl-3′,4′-dimethoxystyryl ketone and methyl methacrylate

Copolymers with various contents of 4-methacryloyloxyphenyl-3′,4′-dimethoxystyryl ketone (MPDSK) and methyl methacrylate (MMA) were prepared in methyl ethyl ketone solution using benzoyl peroxide as a free radical initiator at 70 °C. Characterization of the resulting polymers was done by UV, FT-IR, 1H NMR and 13C NMR spectroscopic techniques. The copolymer compositions were determined by 1H NMR analysis. The monomer reactivity ratios were calculated using linearisation methods such as Finemann–Ross ( r 1 = 0.4283 and r 2 = 0.3050), Kelen–Tudos ( r 1 = 0.4264 and r 2 = 0.2606), and extended Kelen–Tudos ( r 1 = 0.4022 and r 2 = 0.2704) methods as well as by a non-linear error-in-variables model (EVM) method using the computer program RREVM ( r 1 = 0.4066 and r 2 = 0.2802). The molecular weights ( M ¯ w and M ¯ n ) and the polydispersity index of the copolymers were determined by gel permeation chromatography. The thermal stability of the copolymers increases with increase in concentration of MPDSK. Glass transition temperatures were determined by differential scanning calorimeter under nitrogen atmosphere. The photoreactivity of the copolymers having pendant chalcone moieties was studied in chloroform solution.