Porous Polymer Membranes by Hard Templating – A Review

Abstract

Membranes are designed to bridge a precise separation process at the nanoscale with industrial applications running at cubic meters per hour. This review outlines materials applied in membrane production with a particular focus on polymers. Membrane performance and created value are directly linked to controlled pore formation. Their economic relevance has created a number of large companies and associated academic research at top institutions. The authors review, therefore, starts from well-established techniques applied in products and then moves on to evolving concepts from academia. Pore formation through hard templating is a versatile field for separation processes. A more detailed view is given on the two known concepts for nanopore formation, namely colloidal templates and random hard salt templating. A comparison between these two concepts underlines their relevance to combine a process specific separation with large scale manufacturing requirements (i.e., upscale possibility, flexible process control and environmental impact).

Porous functionalized polymers enable generating and transporting hyperpolarized mixtures of metabolites

“…A considerable number of strategies can lead to polymer networks with open porosity of various sizes 44 , 45 , such as selective degradation of block copolymers assembled in co-continuous morphologies 46 , high internal phase emulsions (HIPE) 47 , colloid templating 48 , aerogels or open-cell foams 49 . These methods also share some of the following shortcomings: (i) synthetic complexity or incompatibility of polymerization strategies with the presence of stable radicals; (ii) presence of additives in the materials such as surfactants; or (iii) high temperature or chemical treatments incompatible with the survival of the TEMPO radicals.…”

Dual-template approach to hierarchically porous polymer membranes

“…The process describe here allows for templating at the micron scale, using mild, simple processing conditions. This is advantageous when compared to other templating methods, such as block-copolymer templating 42,43 or particle-guided spinodal decomposition, 44 which require careful control of humidity, evaporation time and template composition to successfully template the desired microstructure, using a multi-step method. The controllable pore structure developed in this work results in properties that are valuable for a variety of applications, for example in membranes for water purification 45 or solar steam generation, [46][47][48] where the increased connectivity allows greater contact of the permeate and the active membrane surface.…”

Porous polymers: structure, fabrication and application

“…In this method, the pore's structures such as size, porosity, shape, and distribution can be effectively regulated by spatial restriction of the templates, ensuring good repeatability and controllability. 138,139 It is evident that the interconnectivity, porosity, and surface area of porous materials increases with the volume fraction of the template. Furthermore, the pore structure of porous scaffolds can be manipulated through the shape, weight fraction, and size of the templates.…”