A biomimetic nanofluidic diode based on surface-modified polymeric carbon nitride nanotubes

A controllable ion transport including ion selectivity and ion rectification across nanochannels or porous membranes is of great importance because of potential applications ranging from biosensing to energy conversion. Here, a nanofluidic ion diode was realized by modifying carbon nitride nanotubes with different molecules yielding an asymmetric surface charge that allows for ion rectification. With the advantages of low-cost, thermal and mechanical robustness, and simple fabrication process, carbon nitride nanotubes with ion rectification have the potential to be used in salinity-gradient energy conversion and ion sensor systems

Colloidal tornadoes in a vial under gravitational sedimentation

Collective motion in living matter is highly intriguing but can also be observed in charged colloidal systems. Collective motion observed in colloidal systems requires extensive material synthesis, external stimuli, and advanced characterization methods that might be highly costly to be employed for teaching. Besides that, colloidal systems can inherently possess dynamic movements. Generally, colloidal sedimentation is pictured as a linear movement, but under certain conditions autonomously activated sedimentation can be attained. In this demonstration, a simple formation of colloidal tornadoes will be explored by gravitational force as the sole stimulus. This demonstration is ideal for the general public for colloid chemistry learning, and these findings can be coupled to colloidal stability lectures

Oxidative photopolymerization of 3,4-ethylenedioxythiophene (EDOT) via graphitic carbon nitride : a modular toolbox for attaining PEDOT

Conductive polymers found key applications ranging from optoelectronics and OLEDs to conductive composite materials. The synthesis of conductive polymers from monomers such as thiophene derivatives, pyrroles and aniline mainly relies on oxidative polymerization, and the processing of so-formed (insoluble) polymers is a major issue that needs to be addressed. In the present work, oxidative photopolymerization of 3,4-ethylenedioxythiophene (EDOT) by visible light employing the metal-free semiconductor graphitic carbon nitride (g-CN) is presented. Two main reaction pathways based on g-CN content will be described, and the formation of processable oligo-EDOT will be demonstrated

On the photopolymerization of mevalonic lactone methacrylate : exposing the potential of an overlooked monomer

Functional polymers remain at the core of polymer science in the second century of macromolecular material research. Lactones are known as monomers for ring-opening polymerizations; however, polymers containing lactone rings as pendant groups are rare. In this study, we revive an overlooked monomer, mevalonic lactone methacrylate, by demonstrating its radical polymerization, reporting the properties of the polymer product, and providing information on the thermal, UV, and hydrolytic stabilities of both the monomer and polymer. Controlled polymerization (via RAFT) provides synthetic precision and active terminal groups; thus, the formation of a simple block copolymer based on the aforementioned polymer is presented. The pendant ring accepts nucleophilic attacks, so the initially hydrophobic polymer can be altered to make it hydrophilic via reactions with nucleophiles in just seconds. Thus, the polymer film provides responsive surface formation

Upgrading poly(styrene-co-divinylbenzene) beads : incorporation of organomodified metal-free semiconductor graphitic carbon nitride through suspension photopolymerization to generate photoactive resins

The inclusion of the metal free semiconductor graphitic carbon nitride (g-CN) into polymer systems brings a variety of new options, for instance as a heterogeneous photoredox polymer initiator. In this context, we present here the decoration of the inner surface of poly(styrene-co-divinylbenzene) beads with organomodified g-CN via one pot suspension photopolymerization. The resulting beads are varied by changing reaction parameters, such as, crosslinking ratio, presence of porogens, and mechanical agitation. The photocatalytic activity of so-formed beads was tested by aqueous rhodamine B dye photodegradation experiments. Additionally, dye adsorption/desorption properties were examined in aqueous as well as in organic solvents. Photoinduced surface modification with vinylsulfonic acid and 4-vinyl pyridine is introduced. Overall, metal-free semiconductor g-CN donates photoactivity to polymer networks that can be employed for dye photodegradation and acid–base catalyst transformation through facile photoinduced surface modifications

Carbon nitride-coated transparent glass vials as photoinitiators for radical polymerization

Benign polymerization routes offer new perspectives in current polymer technology. Especially for automated or continuous flow synthesis of polymers, new devices and principles have to be considered by the means of minimizing addition or separation sequences as well as the type of a polymer initiation. Near-UV and visible light-induced polymerization utilizing metal-free semiconductor polymeric carbon nitride (pCN) as heterogeneous photocatalyst was a first step into this direction. Moving from heterogeneous powder catalysis (which still requests catalyst separation) to surface photocatalysis via coating glass tubes or vials with pCN thin films is presented. Performance and effectivity of those photoactive reactors are proven by free radical photopolymerization of variety of monomers. Reusability of vials is demonstrated via reversible addition-fragmentation chain-transfer polymerization-assisted block copolymer synthesis. This strategy eliminates the necessity of adding or removing initiators, works at room temperature, and offers a platform for cheap and effective polymer synthesis at the age of automated synthesis

Metal-free visible-light-induced dithiol–ene clicking via carbon nitride to valorize 4-pentenoic acid as a functional monomer

The necessity for more bio-based building blocks and processes have led to utilizing new polymerization approaches with a lower carbon footprint. Here, we demonstrate the synthesis of a visible-light-induced dithiol–ene clicking reaction between lignocellulosic biomass-derivable 4-pentenoic acid (4-PEA) and different dithiols, i.e., 1,2-ethanedithiol (EDT), 2,2-(ethylenedioxy)diethanethiol (EDDT), and 1,4-benzenedimethanethiol (BDT), using graphitic carbon nitride (g-CN) as a metal-free photocatalyst. The formation of dicarboxylic acid functional monomers were confirmed using 1H NMR and FT-IR. Furthermore, polyamides were synthesized from the dicarboxylic acid functional monomers to demonstrate the applicability of the monomers yielding new polyamide end polymers

Optical Anisotropy of Carbon Nitride Thin Films and Photografted Polystyrene Brushes

Polymer brushes on surfaces enable advanced material design. In the present contribution, transparent and flat photoactive polymeric carbon nitride (pCN) thin films are employed as a photoactive substrate and primer layer to grow polystyrene (PS) brushes. These films are then characterized by ellipsometry. For the first time herein is reported on the optical anisotropy of pCN thin films revealing a high positive birefringence up to 0.71 with an in-plane nD of 2.54 making this material of high interest for photonic devices. Furthermore and rather surprising, the photografted polystyrene brushes exhibit an unusual high negative birefringence, too. This negative birefringence can be attributed to a practically complete stretching of the polymer chains throughout growth in the radical chain process. As the stretched PS brushes grafted from the pCN surfaces also provide unusual surface properties, the overall system can be of great interest for photonics, but also as mechanical coating and membranes for gas separation

Rainbows in a bottle : realizing microoptic effects by polymerizable multiple emulsion particle design

In nature, structural colour generation is based on discriminative light propagation associated with physical structures in the range of the wavelengths of light1. These iridescent structural colours are of immense significance2 but not easy to control experimentally and therefore difficult to exploit for applications. In this work, we employ microfluidics to produce polymerizable double emulsions that can not only induce the already known lensing effect3 but also result in the spectral separation of white light. Here, liquids of varying refractive in-dex that constitute the emulsions resulted in patterns of iridescent colours. After polymerization, the inner emulsion cores collapse and this results in curved concave surfaces on these polymeric microspheres. Interestingly, the light propagation along the curved surfaces undergo total internal reflection, followed by near-field interference along exit structures on the polymerized microspheres4. These structured polymeric particles that are able to generate colour dispersions can be exploited for optical devices, displays and even sensing technologies