From pH- to Light-Response: Postpolymerization Modification of Polymer Brushes Grafted onto Microporous Polymeric Membranes

Abstract

A microporous pH- and light-responsive membrane that enables remote control over its interfacial properties has been fabricated. pH-Responsiveness was imparted to a porous polypropylene film via grafting of poly(methacrylic acid) brushes from the substrate using argon-plasma-induced free-radical graft polymerization. Morphological changes as a function of grafting level were analyzed using atomic force microscopy. Conversion into a light-responsive membrane was performed via postpolymerization modification to covalently attach photochromic spiropyran moieties to the grafted polymer brushes. Reversible switches in wettability and permeability were determined upon changing from acidic to basic pH or upon alternating UV- and visible-light irradiation. Additionally, light-responsive membranes show a switch in color upon UV exposure.

Explicit Ion Effects on the Charge and Conformation of Weak Polyelectrolytes

“…Though regarded as innately charged, polyelectrolytes frequently contain weakly acidic or basic moieties distributed along the polymer backbone. This can be immensely useful, as monomer groups may protonate or deprotonate depending upon the local environmental conditions, enabling tunable “smart” materials [12,13,14]. Important recent examples include the pH-responsive swelling and collapse of poly(acrylic acid) [PAA] in functionalized nanoporous membranes [15], pH-responsive Saloplastics/Compact polyelectrolyte complexes (COPECs) [16] synthesized using Poly(methacrylic acid) (PMAA) poly(allylamine hydrochloride) (PAH), which find applications in tissue engineering by mimicking mechanical properties of a cartilage [17], self-assembled polyelectrolyte capsules and multilayer thin films for drug delivery purposes [18,19,20].…”

Lamellae—Parking Garage Structure—Lamellae Transition in Densely Grafted Layers of Amphiphilic Homopolymers: Impact of Polymerization Degree

“…It is the maximum possible value indicating the merge of all B groups to the only cluster and the formation of the bicontinuous structure. The ability to pass rapidly from bicontinuous to lamellae structure could be interesting for practical applications which require a quick change of connectivity, such as molecular switches, elements of electrical circuits, the system for controllable catalysis, and so forth . We believe that such types of reconstruction (lamellaeparking garagelamellae) could be observed in other polymer systems, where self-organization is accompanied by the conformation changes of their constituent parts.…”

Light‐Responsive Polymer Membranes

“…Self‐cleaning membranes possess a thin layer of “smart” materials able to respond to the environment changes, improve membrane surface properties, and mitigate fouling . In this approach, photoresponsive materials can be grafted or coated in order to provide switchable and antifouling properties using light as a noninvasive stimulus …”

“…Dübner et al demonstrated a new method for the fabrication of a pH‐ and light‐responsive polypropylene membrane. pH‐responsiveness was imparted via grafting of poly(methacrylic acid) (PMAA) brushes using a plasma‐induced free‐radical graft polymerization.…”