A series of samples with varying cross-linking degree were prepared from the same 1,2polybutadiene-b-polydimethylsiloxane (1,2-PB-b-PDMS) diblock copolymer precursor. The stability of nanopores generated after PDMS cleaving depends on the cross-linking degree of 1,2-PB. The swelling ratio of the crosslinked samples in toluene was converted into a degree of cross-linking following the Flory scheme; a simple relation between the Flory cross-linking degree and the fraction of consumed double bonds during the crosslinking reaction followed. The structure of the block copolymer at different stages of preparation was characterized by small-angle X-ray scattering (SAXS). In addition, scanning electron microscopy (SEM) gave direct images of the nanoporous polymer structure. Nanocavities are accessible to methanol, and observations of methanol uptake were combined with structural information from SAXS. This permits a classification of the bulk cross-linked and etched polymers into three groups: collapsed, traced, and nanoporous materials.

Nanoporous polystyrene with hydrophilic pores was prepared from di- and triblock copolymer precursors. The precursor material was either a poly(tert-butyl acrylate)-b-polystyrene (PtBA-b-PS) diblock copolymer synthesized by atom transfer radical polymerization (ATRP) or a polydimethylsiloxane-b-poly(tert-butyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer synthesized by a combination of living anionic polymerization and ATRP. In the latter copolymer, PS was the matrix and mechanically stable component, PtBA was converted by acidic deprotection to hydrophilic poly(acrylic acid) (PAA) providing at the same time part of the nanoporosity, and PDMS was quantitatively etched to provide additional nanoporosity. Both the deprotection of the PtBA block and the etching of PDMS were realized by one-step operations using either anhydrous hydrogen fluoride (HF) or trifluoroacetic acid (TFA). The finding that TFA can remove PDMS is important, not least as an alternative to the more hazardous HF. The investigated di- and triblock copolymer samples were of either hexagonal or lamellar morphology. The resulting nanoporous polymers were characterized by infrared spectroscopy, small-angle X-ray scattering, and scanning electron microscopy. In contact with water, all the prepared nanoporous polymers showed spontaneous water uptake close to the amounts expected from the precursor block copolymer compositions.

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Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy.

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