The field of 3D printing is continuing its rapid development in both academic and industrial research environments. The development of 3D printing technologies has opened new implementations in rapid prototyping, tooling, dentistry, microfluidics, biomedical devices, tissue engineering, drug delivery, etc. Among different 3D printing techniques, photopolymerization-based process (such as stereolithography and digital light processing) offers flexibility over the final properties of the 3D printed materials (such as optical, chemical, and mechanical properties) using versatile polymer chemistry. The strategy behind the 3D photopolymerization is based on using monomers/ oligomers in liquid state (in the presence of photoinitiators) that can be photopolymerized (via radical or cationic mechanism) upon exposure to light source of different wavelengths (depending on the photoinitiator system). An overview of recent evolutions in the field of photopolymerization-based 3D printing and highlights of novel 3D printable photopolymers is provided herein. Challenges that limit the use of conventional photopolymers (i.e., initiation under UV light) together with prospective solutions such as incorporation of photosensitive initiators with redshifted absorptions are also discussed in detail. This review also spotlights recent progress on the use of controlled living radical photopolymerization techniques (i.e., reversible addition−fragmentation chain-transfer polymerization) in 3D printing, which will pave the way for widespread growth of new generations of 3D materials with living features and possibility for postprinting modifications.

Polyaniline/multiwalled carbon nanotube composite films have been fabricated. It is shown that the nanotubes affect the free N–H environment and quinoid units along the polymer backbone. A 10‐fold increase in conductivity is observed and elemental analysis indicates that the nanotubes compete with chloride ion during HCl doping (see Figure).

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For the first time, we report 3D printing of RAFT-based formulations to fabricate functional objects in a layer-by-layer fashion.

The photopolymerization-based 3D printing process is typically conducted by using free radical polymerization, which leads to fabrication of immutable materials. An alternative 3D printing of polymeric materials by using trithiocarbonate (TTC) reversible addition–fragmentation chain transfer (RAFT) agents has always been a challenge for material and polymer scientists. Herein we report 3D printing of RAFT-based formulations that can be conducted fully open to air using a standard digital light processing (DLP) 3D printer and under mild conditions of visible light at blue (λmax = 483 nm, 4.16 mW/cm2) or green (λmax = 532 nm, 0.48 mW/cm2) wavelength. Our approach is based on activation of TTC RAFT agents using eosin Y (EY) as a photoinduced electron-transfer (PET) catalyst in the presence of a reducing agent (triethylamine (TEA)), which facilitated the oxygen tolerant 3D printing process via a reductive PET initiation mechanism. Reactivation of the TTCs present within the polymer networks enables postprinting monomer insertion into the outer layers of an already printed dormant object under a second RAFT process, which provides a pathway to design a more complex 3D printing. To our best knowledge, this is the first example of oxygen tolerant EY/TEA catalyzed PET-RAFT facilitated 3D printing of polymeric materials. We believe that our strategy is a significant step forward in the field of 3D printing.

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Highly permeable glassy polymeric membranes based on poly (1‐trimethylsilyl‐1‐propyne) (PTMSP) and a polymer of intrinsic porosity (PIM‐1) were investigated for water sorption, water permeability and the separation of CO2 from N2 under humid mixed gas conditions. The water sorption isotherms for both materials followed behavior indicative of multilayer adsorption within the microvoids, with PIM‐1 registering a significant water uptake at very high water activities. Analysis of the sorption isotherms using a modified dual sorption model which accounts for such multilayer effects gave Langmuir affinity constants more consistent with lighter gases than the use of the standard dual mode approach. The water permeability through PTMSP and PIM‐1 was comparable over the water activities studied, and could be successfully modeled through a dual mode sorption model with a concentration dependent diffusivity. The water permeability through both membranes as a function of temperature was also measured, and found to be at a minimum at 80 °C for PTMSP and 70 °C for PIM‐1. This temperature dependence is a function of reducing water solubility in both membranes with increasing temperature countered by increasing water diffusivity. The CO2 ‐ N2 mixed gas permeabilities through PTMSP and PIM‐1 were also measured and modeled through dual mode sorption theory. Introducing water vapour further reduced both the CO2 and N2 permeabilities. The plasticization potential of water in PTMSP was determined and indicated water swelled the membrane increasing CO2 and N2 diffusivity, while for PIM‐1 a negative potential implied that water filling of the microvoids hampered CO2 and N2 diffusion through the membrane. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 719–728