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Early diagnosis of mastitis is essential to reduce the expenses it imparts on the dairy industry. Existing techniques fail to provide rapid and pathogen-specific information to direct the prescript...

Selective control of chemical reactions is critical for the proper regulation of processes ranging from intricate biological systems to large scale industrial manufacturing. The progression of synthetic chemistry toward the complexity seen in Nature requires increased control over many concurrent chemical reactions in a non-interfering (orthogonal) fashion. Fortunately, the practically endless pool of synthetic chemical reactions developed to date can often be combined in an orthogonal manner to provide elegant solutions to complex chemical problems. In this review, we first highlight some of the many photochemical reactions that have been applied in orthogonal reaction protocols; the highly selective nature of photochemical reactions makes them well-suited for independent activation in the presence of other reaction components. The application of these orthogonal reactions, especially photochemical reactions, for the synthesis and modification of polymers and polymeric materials is also summarized. Importantly, the use of orthogonal chemical reactions can provide additional opportunities for synthesizing advanced and functional polymeric materials compared to traditional synthetic procedures.

Dimanganese decacarbonyl (Mn2(CO)10) and alkyl halide combination has unique visible light radical generating property which is useful in the fabrication of many complex macromolecular structures. Herein, we present a generic simple and rapid synthetic approach for the preparation amphiphilic hyperbranched macromolecular structures with controlled branching density and hydrophilicity. The method is based on the visible light induced self-condensing vinyl copolymerization of methyl methacrylate (MMA), 2-(2-bromoisobutryloxy)ethyl methacrylate (BIBEM) and poly(ethylene glycol) methyl ether methacrylate as monomer, inimer and hydrophilic comonomer, respectively, in the presence of Mn2(CO)10. The resulting polymers possess both hydrophobic and hydrophilic sequences offering many potential bio applications such as controlled drug delivery and release. Moreover, the resulting polymers contain also unreacted bromide groups in the final structure which allow postfunctionalization through copper(I)-catalyzed alkyne-azide cycloaddition “click” reactions.

Current food date marking tools fail to take into account variables that impact shelf life, leading to food waste and posing human health risks. Herein, we develop a polydiacetylene/zinc oxide (PDA/ZnO) colorimetric sensor that can indicate milk freshness in real time. The PDA/ZnO system is engineered to indicate the freshness of full cream milk by monitoring its pH based on lactic acid concentration, an indicator of bacterial spoilage. The sensitivity is tuned by selection of the diacetylene monomers from which it is composed. Designs constructed from shorter chain diacetylenes are found to undergo chromatic transitions at a lower lactic acid concentration. Two new methods to tune PDA/ZnO sensitivity to lactic acid are explored, including relocation of the diacetylene functional group and lipid doping. A system constructed from 5,7-hexadecadiynoic acid (HDDA) and ZnO can discriminate between fresh (pH 6.8-6.0), spoiling (pH 6.0-4.5), and spoiled milk (pH 4.5-4.0) by a respective blue to purple to red color change. The chromatic stability of the PDA/ZnO sensor in food is studied as previous reports have shown the system to be unstable. We present a new method that stabilizes the nanocomposite by pre-exposure to the food matrix prior to photopolymerization.

Synthesis of amphiphilic polysulfone graft copolymers by ‘‘Click’’ chemistry is described. First, a commercial PSU was chloromethylated to give chloro-funtional PSU (PSU-Cl). Subsequently, chloride groups were converted into azide moieties by nucleophilic substitution. Hydrophilic poly(N,Ndimethylacrylamide) (PDMA) side chains were then attached via a “grafting to” approach by using coppercatalyzed azide–alkyne cycloaddition (CuAAC). Precursor polymer and the final amphiphilic copolymers were characterized by proton nuclear magnetic resonance ( 1H NMR), fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC) and contact angle measurements.

A straightforward transformation protocol combining two distinct living polymerization methods for the controlled synthesis of block copolymers is described. In the first step, bromo-terminated poly(methyl methacrylate) is prepared by atom transfer radical polymerization (ATRP). Then, a bromide end group is substituted with a triphenylmethyl (trityl) functionality under visible light irradiation using dimanganese decacarbonyl (Mn2 (CO)10 ) photochemistry. The resulting polymers with trityl end groups are used as macroiniferter for the polymerization of styrene and tert-butyl acrylate (tBA) to yield desired block copolymers with narrow molecular weight distribution. Moreover, the amphiphilic copolymers with acrylic acid functionalities are obtained by the hydrolyzation of poly(tert-butyl acrylate) containing block copolymers with trifluoroacetic acid.

Linear poly(hydroxyethyl methacrylate-co-methyl methacrylate) P(HEMA-co-MMA) and poly(dimehylaminoethyl methacrylate-co-methyl methacrylate) P(DMAEMA-co-MMA) and their corresponding hyperbranched copolymers were synthesized by conventional photoinitiated free radical polymerization and self-condensing vinyl polymerization (SCVP) using Type I and Type II photoinitiators, respectively. Then, the polymers were processed by electrospraying in N, N-dimethylformamide. The surface of the resulting electrospray coatings was examined by SEM, XPS, and WCA then compared with those prepared by drop casting. Regardless of the structural nature of the polymers, electrospraying allows the preparation of rough surface that shows more hydrophobic behavior. Electrospray coatings with linear and hyperbranched copolymers exhibited WCA as ∼150° and ∼130°, respectively, indicating that branching reduces the WCA., Istanbul Technical University; Scientific and Technological Research Council of Turkey (TUBITAK)

The synthesis of polyethylene-graft-polystyrene copolymers by a multistep “grafting from” approach is described. In the first step, a bromo-functional polyethylene (PE-Br) was synthesized via ring-opening metathesis polymerization (ROMP) of cis-cyclooctene (COE) and quantitative hydrobromination. Subsequent irradiation of PE-Br under visible light in the presence of dimanganese decacarbonyl (Mn2(CO)10) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) resulted in the formation of TEMPO-substituted polyethylene (PE-TEMPO). Polystyrene (PS) chains were then grown via nitroxide mediated radical polymerization (NMRP) from the PE-TEMPO precursor to give desired PE-g-PS copolymers in a controlled manner. The intermediates at each step and final graft copolymers were characterized by 1H NMR, FT-IR, GPC, and DSC analyses.

A facile strategy for synthesizing block copolymers by the combination of two different living polymerization techniques, namely, photoinduced radical oxidation/addition/deactivation (PROAD) and iniferter processes is described. In the first step, PROAD polymerization of isobutyl vinyl ether using bromotriphenylmethane, dimanganese decacarbonyl (Mn2 (CO)10 ), and diphenyliodonium bromide (Ph2 I+ Br- ) is carried out to yield polymers with triphenylmethyl (trityl) end groups. These prepolymers are used as macroiniferters in thermally induced free radical polymerization of vinyl monomers such as methyl methacrylate, tert-butyl acrylate, and styrene, resulting in the formation of corresponding block copolymers free from homopolymers. The precursor polymer and final block copolymers are characterized by 1 H NMR, FT-IR, GPC, and DSC analyses.

Hyperbranched polymers (HBPs), a unique class of dendritic macromolecules, have received continuous interest from macromolecular scientists due to their inherent properties such as high level of functional terminal units, high solubility, and low viscosity. Despite enormous efforts devoted to the synthesis of HBPs by traditional methods such as single and double monomer strategies involving step-growth polymerization and self-condensing vinyl polymerization (SCVP) processes, there have been limited attempts to employ light-induced processes. Photochemical methods, however, exhibit distinct advantages not characteristically disclosed by traditional ones, such as spatial and temporal control, low energy, and site-specific activation. This review, after a brief summary of the conventional methods, presents the unique features and the key functionalities of the inimers for photoinduced SCVP and strategies for preparing HBPs.

Recent achievements and future opportunities for the design of 2D, 3D, and 4D materials using photochemical reactions are summarized. Light is an attractive stimulus for material design due to its outstanding spatiotemporal control, and its ability to mediate rapid polymerization under moderate reaction temperatures. These features have been significantly enhanced by major advances in light generation/manipulation with light-emitting diodes and optical fiber technologies which now allows for a broad range of cost-effective fabrication protocols. This combination is driving the preparation of sophisticated 2D, 3D, and 4D materials at the nano-, micro-, and macrosize scales. Looking ahead, future challenges and opportunities that will significantly impact the field and help shape the future of light as a versatile and tunable design tool are highlighted.

Type II photoinitiated self-condensing vinyl polymerization for the preparation of hyperbranched polymers is explored using 2-hydroxyethyl methacrylate (HEMA) or 2-(dimethylamino) ethyl methacrylate (DMAEMA), and methyl methacrylate as hydrogen donating inimers and comonomer, respectively, in the presence of benzophenone and camphorquinone under UV and visible light. Upon irradiation at the corresponding wavelength, the excited photoinitiator abstracts hydrogen from HEMA or DMAEMA leading to the formation of initiating radicals. Depending on the concentration of inimers, type of the photoinitiator, and irradiation time, hyperbranched polymers with different branching densities and cross-linked polymers are formed.

Side chain modification of polyolefins applying a copper-mediated “click chemistry” strategy is described. First, a bromo-functionalized polyethylene (PE-Br) are synthesized via ring-opening metathesis polymerization of cis-cyclooctene followed by quantitative hydrobromination. Subsequently, the bromide moieties of the functional PE-based polymer are converted into azide groups via simple nucleophilic substitution. Success of the click reaction is demonstrated by using low molar mass and polymeric alkyne functional click components, namely pyrene alkyne and polystyrene alkyne, respectively. The intermediates at various stages and final polymers are characterized by 1H NMR, Fourier transform infrared, Gel permeation chromatography, and differential scanning calorimetry analysis.

A robust drug delivery system based on nanosized amphiphilic star-hyperbranched block copolymer, namely, poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulting peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin alpha(v)beta(3) receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition toward U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin alpha(v)beta(3) receptor expressing tumor cells.