Photocrosslinking Of Poly Research Articles

A bioactive “self-fitting” shape memory polymer scaffold with potential to treat cranio-maxillo facial bone defects

While tissue engineering is a promising alternative for treating critical-sized cranio-maxillofacial bone defects, improvements in scaffold design are needed. In particular, scaffolds that can precisely match the irregular boundaries of bone defects as well as exhibit an interconnected pore morphology and bioactivity would enhance tissue regeneration. In this study, a shape memory polymer (SMP) scaffold was developed exhibiting an open porous structure and the capacity to conformally “self-fit” into irregular defects. The SMP scaffold was prepared via photocrosslinking of poly(ε-caprolactone) (PCL) diacrylate using a SCPL method, which included a fused salt template. A bioactive polydopamine coating was applied to coat the pore walls. Following exposure to warm saline at T>Ttrans (Ttrans=Tm of PCL), the scaffold became malleable and could be pressed into an irregular model defect. Cooling caused the scaffold to lock in its temporary shape within the defect. The polydopamine coating did not alter the physical properties of the scaffold. However, polydopamine-coated scaffolds exhibited superior bioactivity (i.e. formation of hydroxyapatite in vitro), osteoblast adhesion, proliferation, osteogenic gene expression and extracellular matrix deposition.

Preserved bioactivity and tunable release of a SDF1-GPVI bi-specific protein using photo-crosslinked PEGda hydrogels

Chemokine-induced stem cell recruitment is a promising strategy for post myocardial infarction treatment. Injection of stromal cell-derived factor 1 (SDF1) has been shown to attract bone marrow-derived progenitor cells (BMPCs) from the blood that have the potential to differentiate into cardiovascular cells, which support angiogenesis, enabling the improvement of myocardial function. SDF1-GPVI bi-specific protein contains a glycoprotein VI (GPVI)-domain that serves as an anchor for collagen type I (Col I) and III, which are exposed in the wall of injured vasculature. In this study, we generated a cytocompatible hydrogel via photo-crosslinking of poly(ethylene glycol) diacrylate that serves as a reservoir for SDF1-GPVI. Controlled and sustained release of SDF1-GPVI was demonstrated over a period of 7 days. Release features were modifiable depending on the degree of the crosslinking density. Functionality of the GPVI-domain was investigated using a GPVI-binding ELISA to Col I. Activity of the SDF1-domain was tested for its CXCR4 binding potential. Preserved functionality of SDF1-GPVI bi-specific protein after photo-crosslinking and controllable release was successfully demonstrated in vitro supporting the implementation of this drug delivery system as a powerful tool for therapeutic protein delivery in the treatment of cardiovascular ischemic disease.

Robust anisotropic polymer meshes prepared by stretching and photo-crosslinking of poly(1,2-butadiene) honeycomb films

Anisotropic polymer meshes, which have micrometre-scale rectangular pores, were prepared by simple stretching and photo-crosslinking of poly(1,2-butadiene) honeycomb films. First, honeycomb films with pores of uniform size were prepared by a simple self-organization process. Then, after stretching and UV photo-crosslinking, anisotropic polymer meshes were formed. These anisotropic polymer meshes had high chemical and thermal stability, and exhibited anisotropic wettability. Moreover, by using a photo-crosslinking process, the anisotropic meshes could be photo-patterned. These anisotropic polymer meshes are expected to be applicable to digital microfluidic devices, cell aligners, and other such devices.

Photocrosslinking of poly( N-vinylcarbazole): Implementing a complementary set of techniques to characterize the three-dimensional network formation

The crosslinking of poly( N-vinylcarbazole) PVK resulting from UV irradiation ( λ > 300 nm) was studied by combining various techniques including infrared spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), swelling ratio, positron annihilation spectroscopy (PAS) and thermoporosimetry. The results obtained from all of these techniques were correlated and allowed a complete monitoring of the crosslinking during irradiation, from the creation of the first crosslinks to the formation and densification of the three-dimensional network. From SEC analysis and determination of swelling ratios, it was demonstrated that crosslinking was the predominant mechanism during the first stages of irradiation. PAS and DSC analyses revealed a good correlation between variations of free volume and increase of glass transition ( T g) of the bulk material. In addition, the development of the polymer architecture shown by the growth of T g was nicely correlated with the modifications of the chemical structure observed by infrared analysis. Thermoporosimetry allowed the determination of the mesh size distributions within the polymer for the longest irradiation times. Numerical relationships were established and their validity was checked.

Non-ionic Photoacid Generators Sensitive to 365nm Light-Synthesis and Applications to Photocrosslinking Systems-

Non-ionic photoacid generators (PAG) based on imino sulfonates and N-hydroxyimide sulfonates were designed and synthesized. To obtain the PAGs sensitive to 365 nm light, fluorenone oxime, thioxanthone oxime and N-hydroxyimide derivatives of thioxanthone were used as a chromophore. The PAGs obtained were thermally stable and highly photosensitive. A mechanism for the photolysis of the PGAs was discussed. Some of the thioxanthone-based PAGs were sensitive to 436 nm light. Photocrosslinking of poly(glycidyl methacrylate) using the PAG was also studied.

Photo-Crosslinking of Poly(glycidyl methacrylate) Using Di-functional Photobase Generators

Photo-Crosslinking of Poly(glycidyl methacrylate) Using Di-functional Photobase Generators

Photostability of Poly(Vinyl Chloride)/Poly(Vinyl Alcohol) Blends

Photooxidative degradation and photocrosslinking of poly(vinyl chloride), poly(vinyl alcohol)and their blends with different components ratio has been investigated in accelerated laboratory conditions. It was found that PVC is less photostable than PVAL, in which the photocrosslinking is more efficient. The PVC/PVAL blends have higher photostability comparing to pure PVC but they were less photostable than PVAL alone.

Synthesis and Photocrosslinking of Poly(vinylbenzyl abietate)

Poly(vinylbenzyl abietate) (polyVBA) was synthesized by the polymer reaction of poly(vinylbenzyl chloride) (polyVBC) with sodium abietate in chlorobenzene. The conversion of polyVBC into poly-VBA was very high. The glass transition temperature and initial thermal decomposition temperature of polyVBA were about 122°C and 418°C, respectively. PolyVBA in the film state was found to be crosslinkable via photodi merization of the conjugated carbon-carbon double bonds of the abietic acid moieties.

Design of photoresists with reduced environmental impact. II. Water-soluble resists based on photocrosslinking of poly(2-isopropenyl-2-oxazoline)

The performance of water- and solvent-cast, two-component photoresist films containing poly(2-isopropenyl-2-oxazoline) or poly(2-isopropenyl-2-oxazoline-co-styrene) with a photoacid generator has been investigated. These materials afford negative-tone images after deep-UV exposure and development in a suitable medium (water or toluene). Resist solutions prepared from polymers containing at least 80 mol % 2-isopropenyl-2-oxazoline may be cast from and developed in pure water. Features of higher quality can be obtained when the resist is cast from 2-methoxyethanol, probably because side reactions such as partial hydrolysis of the pendant oxazoline rings in aqueous environments are avoided. It was possible to resolve micrometer scale patterns using ca. 200 mJ/cm2 of irradiation at 254 nm, followed by heating 2 min at 130°C and development in water alone. Image quality and etch resistance were improved using copolymers containing up to 20 mol % of styrene repeat units. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1225–1236, 1999

Photocrosslinking of Poly(4-hydroxystyrene) via Electrophilic Aromatic Substitution: Use of Polyfunctional Benzylic Alcohols in the Design of Chemically Amplified Resist Materials with Tunable Sensitivities

The use of polyfunctional benzylic alcohols as latent cationic cross-linkers for polymers such as poly(4-hydroxystyrene) has been explored. Photogeneration of acid within thin films of the phenolic resin containing the latent cross-linker results in their thermal cross-linking via electrophilic aromatic substitution in a self-perpetuating process. This cationic photo-cross-linking reaction has been used to design resist materials that show remarkably high sensitivities in the three common modes of lithography: deep-UV (0.2 mJ/cm 2 ), E-beam (0.1 μC/cm 2 ), and X-ray (<10 MJ/CM 2 )

Photocrosslinking of poly( n-phenylmethacrylamide) and its homologues

Polymers bearing N-arylamide units in the side-chains were synthesized by the radical polymerization of N-phenylmethacrylamide (PhMA) and its homologues; the photocrosslinking behaviour of the polymers was studied. When the polymers were irradiated with u.v. light, they became insoluble. The substituents on the phenyl ring of PhMA units and the glass transition temperatures of the polymers strongly affected the efficiency of the photocrosslinking. It was found that the 2′- and 4′-aminoacetophenone moieties, formed by the photo-Fries rearrangements of PhMA units, participated in the photocrosslinking; 4′-aminoacetophenone moieties were more important than 2′-aminoacetophenone moieties for the photocrosslinking. A reaction mechanism is discussed.

Organic sulphur compounds as initiators of polymerization. Part IV. Photocrosslinking of poly(2,3-epoxypropyl methacrylate) with sulphur-containing a zocom pounds

Organic sulphur compounds as initiators of polymerization. Part IV. Photocrosslinking of poly(2,3-epoxypropyl methacrylate) with sulphur-containing a zocom pounds

Photocross-linking of polymers initiated by benzylsulphonium salts as cationic initiators

Photocross-linking of poly(1,3-dioxolane-4-methyl methacrylate) and copolymers with methyl methacrylate initiated by benzylsulphonium salt (BSS) has been explored. On photoirradiation, BSS directly produces benzyl cations which are capable of initiating cationic polymerization of side-chain cyclic ketals. The homopolymer and the copolymers were doped with BSS in the concentration range 0.05-5 mol% on the basis of the ketal units and the resulting films were irradiated at >300 nm in air

Polymères photoréticulables à unités cinnamiques, 3. Photoréticulation

AbstractPhotocrosslinking of polymers, prepared from cinnamic acid derivatives, by chemical modification of poly(vinyl alcohol) or polycondensation of difunctional cinnamic acid derivatives has been studied. With Michler's ketone (sytem. name: 4,4′‐bis(dimethylamino)benzophenone), crosslinking of copolymers is improved. 2‐Nitrofluorene or 9‐xanthenone have little effect on the crosslinking rate. Photocrosslinking of poly(α‐cyano‐4‐vinylcinnamic acid), poly(ethyl α‐cyano‐4‐vinylcinnamate) and their copolymers is enhanced in the presence of 2‐hydroxy‐2‐methylpropiophenone, but the effect is lowered in the case of its acrylic esters or their (co)polymers.

Photo-chemical behaviour of poly(organophosphazenes): Part VI—Photo-stabilization of poly[bis(4-benzoylphenoxy)]phosphazene by energy transfer processes

Photo-degradation and photo-crosslinking of poly[bis(4-benzoylphenoxy)]-phosphazene, [NP-(-O-C 6H 4-CO-C 6H 5) 2] n′ originates from the first excited triplet state of the benzophenone moiety appended to the phosphazene polymer backbone. Both reactions can be inhibited by energy transfer processes to suitable energy acceptors. Evidence is given that both free naphthalene and naphthalene attached to the cyclophosphazene ring are able to quench the photo-reactivity of the benzophenone-supporting phosphazene polymer.

Photocrosslinking of poly(2,3‐epithiopropyl methacrylate) by the oxidation of pendant episulfide groups

AbstractIn the photocrosslinking of poly(2,3‐epithiopropyl methacrylate) (PETMA) films the effect of the pendant episulfide group's oxidation on the crosslinking of PETMA was investigated. Thermal crosslinking of PETMA is promoted by peroxides such as benzoyl peroxide and hydrogen peroxide. IR spectrum of the crosslinked PETMA showed that the reaction proceeded through the oxidation of episulfide groups by the peroxides. The anthracene (An) sensitized photocrosslinking of PETMA films also proceeded via the oxidation of episulfide groups by singlet oxygen. It was found that residual tetrahydrofuran (THF) in the films remarkably increased the rate of the photocrosslinking and/or reduced the induction period. From the further investigation concerning casting solvents it was found that residual CS2, CCl4, and CHCl3 in films increased the rate of the photocrosslinking and/or reduced the induction period of the photocrosslinking. The disappearance rate of An in the films was also increased by the presence of residual CS2, CCl4, and CHCl3, differring from the result of THF. These results were explained by a difference in lifetime of singlet oxygen in the films. From the results were explained by a difference in lifetime of singlet oxygen in the films. From the results concerning the effects of hydroperoxides such as THF hydroperoxide and t‐butyl hydroperoxide on the photocrosslinking of PETMA films the acceleration effect of the residual THF was deduced to be due to the promotion of singlet oxygen‐oxidation of sulfide groups by protic compounds such as THF hydroperoxide and H2O in the THF.

Photo‐Crosslinking of poly(2,3‐epoxypropyl methacrylate) with imino sulfonates

Photo‐Crosslinking of poly(2,3‐epoxypropyl methacrylate) with imino sulfonates

1,1′‐(2,6‐naphthalenedicarbonyl)Diaziridine as a useful agent for photocrosslinking of poly(4‐hydroxystyrene) in film

1,1′‐(2,6‐naphthalenedicarbonyl)Diaziridine as a useful agent for photocrosslinking of poly(4‐hydroxystyrene) in film

Photocrosslinking of poly(2,3‐epithiopropyl methacrylate) and its copolymers

Photocrosslinking of poly(2,3‐epithiopropyl methacrylate) and its copolymers

Photocrosslinking of poly (2,3‐epoxypropyl methacrylate) films with organic sulfur compounds

Photocrosslinking of poly (2,3‐epoxypropyl methacrylate) films with organic sulfur compounds