For the next generation of handling systems, reversible adhesion enabled by micropatterned dry adhesives exhibits high potential. The versatility of polymeric micropatterns in handling objects made from various materials has been demonstrated by several groups. However, specimens reported in most studies have been restricted to the laboratory scale. Upscaling the size and quantity of micropatterned adhesives is the next step to enable successful technology transfer. Towards this aim, we introduce a continuous roll-to-roll replication process for fabrication of high-performance, mushroom-shaped micropatterned dry adhesives. The micropatterns were made from UV-curable polyurethane acrylates. To ensure the integrity of the complex structure during the fabrication process, flexible templates were used. The compression between the template and the wet prepolymer coating was investigated to optimize replication results without structural failures, and hence, to improve adhesion. As a result, we obtained micropatterned adhesive tapes, 10 cm in width and several meters in length, with adhesion strength about 250 kPa to glass, suitable for a wide range of applications.

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ABSTRACT:On the basis of so-called linear free enthalpy correlations, a method is developed to predict vinyl contents of polybutadienes from anionic polymerizations with butyllithium in nonpolar solvents in the presence of bases. According to Reichardt with an extension by Langhals, a transition energy scale for the solvatochromic dye N,Ndimethyl indoaniline in dependence of concentrations of some bases is established. The bases were taken from polymerizations of butadiene of Antkowiak et al. and of Jin et al. It could be shown that vinyl contents determined by these authors correlate well with measured transition energies over the whole concentration range of the bases. Also, temperature dependences of vinyl contents can be predicted satisfactorily. Furthermore, it was found that vinyl contents in polybutadienes depend for weak bases primarily on the polarity of the solution mixture determined by the base concentration and not on the molar ratio of base to initiator. The results are extensively discussed in comparison with earlier attempts in the literature to predict the microstructure in polybutadienes in dependence of polar modifiers.

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