Photografting-surface

J. Balart, V. Fombuena, J.M. Espana, L. Sanehez-Nacher, R. Balatt, Improvement of adhesion properties of polypropylene substrates by methyl methacrylate UV photografting surface treatment. Mater. Des. 33, 1-10 (2012)... 

N-vuiylpyrrolidone, diffd-ential UV spectroscopy, photografting, surface modification. 

UV light in a second step. In later work reported by Tazuke, Kimura et al. (6-8) successful photograftings on the polymer surface of thin films (polyethylene, polypropylene and polystyrene) were achieved with various monomers. In this work, grafting was induced by UV irradiation through the film which was in contact with a solution containing initiator and monomer. The method is slow and - in addition to surface grafting - large amounts of homopolymer are formed. 

In our surface photografting research we have developed two new processes applied to sheets, films and fibers of polyethylene (PE), polypropylene (PP) and poly(ethylene-terephthalate) (PET). 

Photografting of Acrylic Monomers onto Polyolefin Surfaces... 

Surface Modifications. Basic photopolymer chemistry is also being used for the surface modification of films, textiles fibers, and many other organic-based materials (104). Some of the novel applications of photopolymer technology to surface modification include the design of cell repellent treatments and in photografting of various chemical functionality onto the surface of materials to improve color retention, enhance the adhesion of antistatic chemicals or to improve staining resistance. 

The prototype of the present surface photografting is the surface photoreaction of maleic anhydride(MAH) onto poly(butadiene) film(15). Although fair improvement of surface wettability was achieved, photoaddition of MAH cannot be applied to other polymers having no ethylenic double bonds. The present process is applicable to almost all polymers except for poly(tetrafluoroethy-lene) and its analogues. 

Figure 1. Surface photografting apparatus (a) 100W high-pressure Hg lamp (b) interference filter (c) borosilicate glass plate (d) reacting solution (e) polymer film (f) glass vessel (g) clamp screw (17)...

Table 2 Durability Test of Grafted Polymer Surface. Sample Polypropylene Film Photografted with Acrylamide(16)...

Choice of sensitizer is related to the base polymer properties. Besides triplet sensitizers, dyes(4, 5), metal salts(11, 12), and radical initiators(7, 11, 12) have been used in photografting. These sensitizers other than triplet sensitizers are, however, not capable of initiating surface photografting onto polyolefins. Although benzoin isopropyl ether has been used for photografting of polypropylene, the reaction conditions seem to be in favor of deep grafting(12). 

Time-Conversion Profile of a Surface Photografting System,... 

For internal graft polymerization or grafting on to polymers reactive to radical attack, inhibition by oxygen is not a serious problem. However, surface photografting of polyolefins in an open system is very inefficient. The results in Figure 13 indicate that oxygen diffused through or in OPP film is an efficient retarder. 

Table Base Solvents (S) 4. Summary of Solvent Film 0PP, Monomer AM, S - 0PP BP 3 + S interaction reaction Effects on Surface Photografting. Sensitizer BP, Irradiation at 366nm. Surface Rate of Proposed structure concentration grafting of grafted 0PP film of polyAM ...

Table 5. Improved paintability of Polystyrene Plate Treated by Surface Photografting Method.

Piletsky SA, Matuschewski H, Schedler U, Wilpert A, Piletska EV, Thiele TA, Ulbricht M. Surface functionalization of porous polypropylene membranes with molecularly imprinted polymers by photograft copolymerization in water. Macromolecules 2000 33 3092-3098. 

Wang HY, Kobayashi T, Fujii N. Surface molecular imprinting on photosensitive dithiocar-bamoyl polyacrylonitrile membranes using photograft polymerization. J Chem Technol Biotechnol 1997 70 355-362. 

Fig. 16 Representative f-d curves measured for photograft-polymerized surfaces of DMA after photoirradiation for 10 s, 20 s, 1 min, 5 min, 10 min, and 20 min. Dashed curves Approaching trace, solid curves retracting trace. The repulsion interaction distance increased with photoirradiation time...

Fig. 17 a Dependence of the repulsive interaction distance between the albumin (Alb)-fixed tip and the photograft-polymerized surface of DMAm on the photoirradiation time. A magnification of the plot within 60 s is shown in the inset, b Dependence of compressive force of the DMAAm graft-polymerized layer on its compression deformation... 

A two-dimensional micropatterned tissue can be easily obtained by utihz-ing the inherent differences in cell adhesiveness between different micropatterned photografted regions. This was attained by photoiniferter graft polymerization with a projection mask placed on an iniferter-derivatized surface. Since protein adsorption and cell adhesion are markedly suppressed on nonionic graft polymers, such as polyDMAm, any anchorage-dependent cells such as endothelial cell adhere and proliferate only on nonirradiated surfaces, resulting in the formation of a two-dimensional patterned tissue or cellular sheet (Fig. 24). 

Fig. 25 Schematic diagram of the presentation of a regionally specific micropatterned surface with an unprecedented five different photograft-copolymerized regions using the comhination of a photomask and an X-Y step motor-controUed stage...

Fig. 26 Schematic diagram of the preparation of a gradient surface varying unidirection-ally in thickness of the photograft-copolymerized layer by using the combination of two types of photomasks and the X-Y step motor-controlled stage...

Fig. 27 AFM sampling locations of the grafted region (1) and surface topological featiu-es of photograft-copolymerized surfaces as observed by AFM (2). AFM images of the gradient surface regions at 200 jjim (position e in 1) (2A) and 1100 jjim (position b in 1) (2B), which correspond to irradiation times of 13.5 and 6.75 min, respectively. Line scan spectra for selected regions corresponding to those in part 1 of the gradient film show the measured film thickness...

---