Off-stoichiometry thiol-ene polymer

After complete polymerization, typically by UV micromolding, the polymer articles contain a well-defined number of unreacted thiol or allyls groups both on the surface and in the bulk.

[3] The OSTE polymer resins were originally developed by Tommy Haraldsson and Fredrik Carlborg at the group of Micro and Nanosystems[4] at the Royal Institute of Technology (KTH) to bridge the gap between research prototyping and commercial production of microfluidics devices.

The thiols and allyls react in a perfectly alternating fashion and has a very high conversion rate (up to 99%),[5] the initial off-stoichiometry of the monomers will exactly define the number off unreacted groups left after the polymerization.

[8][1] The glass transition temperature typically varies from below room-temperature for high off-stoichiometric ratios to 75 °C for a stoichiometric blend of tetrathiol and triallyl.

The advantages put forward for the OSTE+ are i) their unique ability for integration and bonding via the latent epoxy chemistry and the low built-in stresses in the thiol-enes polymers[13] ii) their complete inertness after final cure iii) their good barrier properties[14] and the possibility to scale up manufacturing using industrial reaction injection molding.

[15] Both stiff and rubbery versions of the OSTE+ polymers have been demonstrated, showing their potential in microsystems for valving and pumping similar to PDMS components, but with the benefit of withstanding higher pressures.

[29] Imprinting of arrays with hydrophilic-in-hydrophobic microwells is made possible using an innovative surface energy replication approach by means of a hydrophobic thiol-ene polymer formulation.