Poly contact angle changes

Figure 2. Contact angle changes with various liquids on a film of poly (methyl methacrylate) irradiated in air...

Figure 2.18 Contact angle changes of PLAioo and PLAq films with immersion time in pH = 8.6 Tris buffer containing proteinase K at 25°C. PLA, poly(lactic acid).

Figure 4.6 Contact angle changes of poly(trimethylene carbonate) (PTMC) during immersion in phosphate buffer containing 0.2 mg/mL lipase CA, and of P(TMC-co-GA) 84/16 (PTGA) during immersion in phosphate buffer containing 0.2 mg/mL lipase HP. CA, Candida antarctica-, HP, Hog pancreas.

Styrene) (PPFS), poly(heptadecafluorodecyl acrylate) (PHFA), poly(penta-fluoropropyl acrylate) (PPFA), or poly(trifluoroethyl acrylate) (PTFA) [53]. The block at the silicate interface was either PS or PMA. Treatment of the diblock systems with block-selective solvents produced predictable changes in water contact angles except for those diblock brushes based on PHFA. All of these systems were fully characterized by XPS, tensiometry, ellipsometry,... 

The effect of ultraviolet irradiation in air on the wettability of thin films of amorphous polymers has been studied. With poly(vinyl chloride), poly(methyl methacrylate), poly(n-butyl methacrylate), poly (ethylene terephthalate), and polystyrene the changes in contact angles for various liquids with irradiation time are a function of the nature of the polymer. A detailed study of polystyrene by this technique and attenuated total reflectance spectra, both of which are sensitive to changes in the surface layers, indicates that the contact angle method is one of the most sensitive tools for the study of polymer photooxidation in its early stages. The method is useful in following specific processes and in indicating solvents to be used in the separation and isolation of photooxidation products. 

That photooxidation is indeed responsible for the observed changes is indicated by a comparison with the results obtained with films irradiated in vacuum. Both polystyrene and poly(n-butyl methacrylate) irradiated in vacuum showed no changes in contact angles after exposures up to 120 min. with poly (ethylene terephthalate), contact angles for all of the liquids tended to increase slightly. 

Here we report a wet surface modification of PMDA-ODA and poly-(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) with KOH or NaOH solution. The modified surfaces are identified with contact angles, XPS spectra and ER IR spectra. Polymer thickness and weight changes are also studied. The depth of modified layer is measured by a non-destructive technique using ER IR and ellipsometry. Relationship between surface structure and adhesion strength is discussed. 

Figure 4.8. Change of the advancing contact angle against water in the blend of a PDMS graft copolymer in poly(methyl methacrylate).

The bonding of a viscoelastic material (a film of glue) onto a solid surface can only be expected, then, when the surface tension of the liquid is lower than the critical surface tension 7. of the solid body. According to equation (13-3), these two quantities are related to the contact angle S and the interfacial surface tension between solid and adhesive film. Since a chemical variation in the surface can also cause the surface tension to change, it is often possible to obtain better bonding through chemical modification of a surface. An example of this is the oxidation of the surface of polyolefins [see the critical surface tensions of poly(ethylene) and poly-(vinyl alcohol) in Table 13-3]. 

---