Thermo-Switchable Pressure-Sensitive Adhesives Based on Poly(N-vinyl caprolactam) Non-Covalently Cross-Linked by Poly(ethylene glycol)

Abstract

The properties of new hydrophilic pressure-sensitive adhesives (PSA) obtained by blending poly(N-vinyl caprolactam) (PVCL) with short-molecular weight poly(ethylene glycol) (PEG) were studied in aqueous media by a combination of several calorimetric and adhesion testing techniques. We found that the adhesive properties of the blends are the result of an extensive hydrogen bonding network formed between PVCL and PEG similar to the poly(N-vinylpyrrolidone) (PVP)/PEG blends, except the extent of cross-linking is nearly 3 times higher in PVCL−PEG networks. Accordingly, we observed substantially higher peel adhesion in PVCL−PEG blends, which depends strongly on the amount of adsorbed water and the temperature. The adhesive properties of PVCL−PEG gels are considerably diminished when the amount of absorbed water exceeds 30% or at elevated temperature but can be easily recovered by drying or cooling the sample. The observed responsiveness of PVCL−PEG hydrogels in physiologically relevant temperature range makes them interesting candidates for industrial and biomedical applications as smart PSAs.

Pressure sensitive adhesives based on interpolymer complexes

“…The negative T g deviations for the PVCL -PEG blends were found to be about 25 -30 o C greater than those for the PVP -PEG system at comparative contents of PEG-400 [43]. It is therefore no wonder that the content of noncovalently crosslinked PNVAm units through PEG-400 chains, shown in Figure 13 for PVCL-PEG and PVP-PEG blends, is remarkably independent of PEG content within a wide composition range, which is direct evidence of the non-equimolar Figures 11C and 12), i.e.…”

“…However, negative deviations from the Fox equation in the PVCL blends with PEG-400 are appreciably larger, than those for the PVP -PEG system [43].…”

“…It is therefore no wonder that the content of noncovalently crosslinked PNVAm units through PEG-400 chains, shown in Figure 13 for PVCL-PEG and PVP-PEG blends, is remarkably independent of PEG content within a wide composition range, which is direct evidence of the non-equimolar Figures 11C and 12), i.e. three times lower than in PVCL-PEG blends (see Figure 13, [43]). …”

“…Our earlier research established that blends of high molecular weight, glassy poly(N-vinyl amides) (PNVAm), such as poly(N-vinyl pyrrolidone) (PVP, M w =1,000,000 g/mol; M n =360,000 g/mol) [39,42] or poly(N-vinyl caprolactam) (PVCL) [43], with liquid poly(ethylene glycol) (PEG, M w =400 g/mol) demonstrate excellent pressure sensitive adhesion [38,39,42,43]. PVP has been shown to be easily soluble in low molecular weight PEG, yielding single phase homogeneous blends [44][45][46].…”

Characterization of an acrylic polymer under hygrothermal aging as an optically clear adhesive for touch screen panels

“…The nitrogen atom in an NVC structure has high electronegativity; therefore, NVC can help enhance the cohesion of OCAs. NVC has been employed in other studies for medical pressure sensitive adhesives (PSAs) [3,4], self-adhesive products, such as labels [5,6], drug delivery systems [7], and dental materials [8].…”