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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.

A new polymerization mechanistic transformation strategy, combining two different controlled polymerization techniques of different modes, atom transfer radical polymerization (ATRP) and photoinduced radical oxidation/addition/deactivation (PROAD), is successfully applied for the synthesis of block copolymers. Thus, mono- or bi- bromide functional polystyrenes (PS-Br or Br-PS-Br) synthesized by light induced ATRP were used as macroinitiator for the living cationic polymerization of isobutyl vinyl ether via PROAD process to give the corresponding block copolymers. In this way, depending on the structure of the macroinitiator, AB or ABA type block copolymers (PS-b-PIBVE or PIBVE-b-PS-b-PIBVE) were formed. The final polymers and precursor polymers were characterized by spectral and chromatographic analyses.

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.

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.

A novel polymerization mechanism transformation strategy, combining ring-opening metathesis polymerization (ROMP) and visible light induced cationic polymerization, is successfully applied for the synthesis of polyethylene-graft-poly(cyclohexene oxide) (PE-g-PCHO). First, cis-cyclooctene (COE) was polymerized via ROMP in the presence of a chain transfer agent and quantitatively hydrobrominated to give bromo functional polyethylene (PE-Br). Subsequent irradiation of PE-Br in the visible range using dimanganese decacarbonyl (Mn-2(CO)(10)) and diphenyl iodonium hexafluorophosphate (Ph2I+PF6) as radical generator and oxidant, respectively, initiated cationic polymerization of cyclohexene oxide (CHO) resulting in the formation of PE-g-PCHO. The effect of irradiation time and Mn-2(CO)(10) concentration on the grafting density and efficiency was evaluated. Both the precursor polymers and the corresponding graft copolymers were characterized by H-1 NMR and Fourier transform infrared (FT-IR) spectroscopy, gel-permeation chromatography (GPC), and differential scanning calorimetric (DSC) analyses.

In the present study, two amphiphilic star-hyperbranched copolymers based on poly(methyl methacrylate)-b-poly(2-hydroxyethyl methacrylate) (PMMA-b-PHEMA), with different hydrophilic PHEMA segment contents (PMMA-b-PHEMA-1, and PMMA-b-PHEMA-2), were synthesized, and their drug loading and release profiles were examined using Paclitaxel (PTX) as a model drug. The drug loading capacities and encapsulation efficiencies were found to be similar in both polymers. The encapsulation efficiencies were found to be prominent at 98% and 98.5% for PMMA-b-PHEMA-1 and PMMA-b-PHEMA-2, respectively. On the other hand, the drug release behaviors varied in favor of the block copolymer comprising shorter PHEMA chains (PMMA-b-PHEMA-1). Additionally, to assess the biological effects of PTX-loaded polymers, human non-small cell lung carcinoma (A549) cells were used. Cell viability and cell cycle analysis showed that both polymers were non-toxic to cells. The cytotoxic effect of PTX-loaded PMMA-b-PHEMA-1 on A 549 cells was greater (66.49% cell viability at 5.0 ng mL(-1) PTX) than that of PMMA-b-PHEMA-2 (72.47% cell viability at 5.0 ng mL(-1) PTX), consistent with the drug release experiments.

A simple approach for the preparation of a clickable poly(ethylene glycol)-based hydrogel as a polymeric support for protein immobilization via photoinitiated free radical polymerization of poly(ethylene glycol) diacrylate and propargyl acrylate is established. Bioconjugation to the obtained gels was achieved by azide–alkyne click reaction with azido-functionalized anti-immunoglobulin G (anti-IgG) and anti-His tag antibodies. Evaluation of the affinities of the PEG hydrogels to the corresponding substrates (IgG and His-tagged YFP, respectively) indicates their specific binding capability.

A facile synthesis method for the preparation of clickable hydrogels and linear polymers is described. The strategy pertains to the photochemical generation of initiating radicals by hydrogen abstraction of excited camphorquinone from acetylenic alcohol followed by free radical polymerization. For hydrogels, poly(ethylene glycol) methyl ether methacrylate and poly(ethylene glycol) diacrylate were used in the system as monomer and crosslinker, respectively. Fluorescent pyrene groups were anchored onto the hydrogels through copper-catalyzed Huisgen 1,3-dipolar azide/alkyne click reaction by using 2-azidomethyl pyrene as evidenced by Fourier transform infrared and fluorescence spectroscopy. The applicability of the method for macromolecular synthesis is also demonstrated. For this purpose, poly(methyl methacrylate) with alkyne terminal groups was prepared by photoinitiated free radical polymerization of methyl methacrylate using camphorquinone and 3-(trimethylsilyl)propargyl alcohol as sensitizer and hydrogen donor, respectively. After deprotection, the click reaction with azido polystyrene obtained by atom transfer radical polymerization followed by azidation resulted in the formation of polystyrene-b-poly(methyl methacrylate). The intermediates at various stages and the final block copolymer were characterized by spectral analysis and gel permeation chromatography. © 2014 Society of Chemical Industry

Visible light induced self-condensing vinyl polymerization is explored using 2-bromoethyl methacrylate (2-BEMA) and methyl methacrylate (MMA) as inimer and comonomer, respectively, in the presence of dimanganese decacarbonyl (Mn2(CO)10) for the preparation of hyperbranched polymers. Upon photoexcitation in the visible range, Mn2(CO)10 undergoes irreversible decomposition leading to the formation of initiating radicals through bromine abstraction from 2-BEMA. Depending on the concentrations of 2-BEMA and Mn2(CO)10 and irradiation time, hyperbranched polymers with different branching density and cross-linked polymers were formed. The resulting polymers possess unreacted bromide groups in the structure which allow postfunctionalization through visible light photopolymerization and Cu(I)-catalyzed click reactions.

Polyethylene-graft-poly(tert-butylacrylate) (PE-g-PtBA) copolymers were prepared by using a combination of ring-opening metathesis polymerization (ROMP), hydrobromination, and visible light-induced free radical polymerization. First, cis-cyclooctene was polymerized via ROMP in the presence of a chain transfer agent and quantitatively hydrobrominated. Poly(tert-butyl acrylate) (PtBA) chains were then grown via a grafting from approach from the Br-substituted linear poly(ethylene) (PE) backbone using dimanganese decacarbonyl (Mn2(CO)10) under visible light. The effect of Mn2(CO)10 concentration and irradiation time on the grafting density and efficiency was evaluated. The tert-butyl acrylate (tBA) esters of the graft copolymers were hydrolyzed into acrylic acid functionalities by acidolysis to obtain hydrophilic polyolefins. The precursor polymer, graft copolymer, and hydrolyzed polymer were characterized by 1H and 13C NMR, Fourier transform infrared, atomic force microscopy, and contact angle measurements.

Visible light-induced reverse and simultaneous reverse and normal initiation (SR&NI) atom transfer radical polymerizations of vinyl monomers are examined using various dyes and type I photoinitiators. The effect of photoinitiator types on the control of molecular weight and distribution is described. In both dye and type I photoinitiator sensitized SR&NI ATRP systems, the molecular weights increase linearly with conversion. However, the experimental molecular weights are considerably higher than the theoretical values and the polymers show broad-molecular-weight distributions ranging from 1.28 to 1.60 in the dye-sensitized SR&NI ATRP. However, the polymers obtained by SR&NI ATRP using type I photoinitiator system had molecular weight values close to the theoretical ones and very narrow-molecular-weight distributions ranging from 1.11–1.18.

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.

Lightly branched, hyperbranched and cross-linked polymers with clickable sites were synthesized via a modified version of self-condensing photoinitiated copolymerization of methyl acrylate (MA) with propargyl acrylate (PA). The method is based on the use of a PA monomer containing two polymerizable groups, namely acrylate and propargyl groups with different reactivities in photoinitiated free radical copolymerization with MA.

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.