Highly Ordered Nanoporous Thin Films from Photocleavable Block Copolymers

Abstract

Poly(styrene-block-ethylene oxide) with an o-nitrobenzyl ester photocleavable junction (PS-hν-PEO) was synthesized by a combined RAFT polymerization and “click chemistry“ approach and represents the first report utilizing this method for the synthesis of photocleavable block copolymers. After solvent annealing, highly ordered thin films were prepared from PS-hν-PEO. Following a very mild UV exposure and successive washing with water, PS-hν-PEO thin films were transformed into highly ordered nanoporous thin PS films with pore diameters of 15–20 nm and long range ordering (over 2 μm × 2 μm). Afterwards the pores were filled with PDMS by spin-coating in combination with capillary forces. After treatment with oxygen plasma to remove the PS templates, highly ordered arrays of silica nanodots were obtained. This represents the first template application example from highly ordered nanoporous thin films derived from block copolymers featuring a photocleavable junction.

Light‐Triggered Multifunctionality at Surfaces Mediated by Photolabile Protecting Groups

“…[ 125 ] (PEO) containing a photocleavable o -nitrobenzyl junction ( Figure 15 ). [133][134][135][136] Spin-coated fi lms formed patterns of PEO nanodots in a PS matrix. Upon irradiation, a rinsing step in water/methanol mixture dissolved the PEO block and left a nanostructured PS fi lm with homogenous nanopores at the surface.…”

Pattern transfer using block copolymers

“…A methanol-water (10 : 1) solvent mixture served to rinse the degraded PS-b-PEO film, and dissolved the cleaved PEO domains, leaving a porous PS template for further patterning applications. O-nitrobenzyl ester, a photo-cleavable junction, was synthesized between PS and PEO domains by RAFT polymerization [73]. This makes PS-b-PEO degradable under 365 nm UV light (dose of 5.6 J cm 2 ), and it behaves similarly to PS-b-PMMA but with a higher Flory-Huggins interaction parameter.…”

Polyurea microcapsules with a photocleavable shell: UV-triggered release

“…18 o-Nitrobenzyl based functional groups have been used to design different photodegradable polymeric systems such as bulk hydrogels 19,20 , microgels 21 , photo-cleavable block copolymers [22][23][24][25] and micelles 26 . Recently, they gained further interest as protecting group in the UV-responsive release of certain functional groups such as thiols.…”