Facile Synthesis of Well-Defined MDMO-PPV Containing (Tri)Block—Copolymers via Controlled Radical Polymerization and CuAAC Conjugation

Abstract

A systematic investigation into the chain transfer polymerization of the so-called radical precursor polymerization of poly(p-phenylene vinylene) (PPV) materials is presented. Polymerizations are characterized by systematic variation of chain transfer agent (CTA) concentration and reaction temperature. For the chain transfer constant, a negative activation energy of −12.8 kJ· mol −1 was deduced. Good control over molecular weight is achieved for both the sulfinyl and the dithiocarbamate route (DTC). PPVs with molecular weights ranging from thousands to ten thousands g· mol −1 were obtained. To allow for a meaningful analysis of the CTA influence, Mark-Houwink-Kuhn-Sakurada (MHKS) parameters were determined for conjugated MDMO-PPV ([2-methoxy-5-(3',7'-dimethyloctyloxy)]-1,4-phenylenevinylene) to α = 0.809 and k = 0.00002 mL· g −1 . Further, high-endgroup fidelity of the CBr4-derived PPVs was proven via chain extension experiments. MDMO-PPV-Br was successfully used as macroinitiator in atom transfer radical polymerization (ATRP) with acrylates and styrene. OPEN ACCESSPolymers 2015, 7 419A more polar PPV counterpart was chain extended by an acrylate in single-electron transfer living radical polymerization (SET-LRP). In a last step, copper-catalyzed azide alkyne cycloaddition (CuAAC) was used to synthesize block copolymer structures. Direct azidation followed by macromolecular conjugation showed only partial success, while the successive chain extension via ATRP followed by CuAAC afforded triblock copolymers of the poly(pphenylene vinylene)-block-poly(tert-butyl acrylate)-block-poly(ethylene glycol) (PPV-bPtBuA-b-PEG).

PPV Polymerization through the Gilch Route: Diradical Character of Monomers

“…Interestingly,i narecent experimental study by some of the authors, the activation energy of propagation based on chain-transfer polymerization was estimated to be around 30 kJ mol À1 . [45] The formation of paracyclophane-side reaction Instead of furtherp ropagating to give PPV,t he "packed" radical dimer Int2(T) could undergo an intramolecular recombination reaction to form as ide product, that is, [2.2]paracyclophane ( Figure 3).…”

PPV-Based Conjugated Polymer Nanoparticles as a Versatile Bioimaging Probe: A Closer Look at the Inherent Optical Properties and Nanoparticle–Cell Interactions

“…Both PPVs were synthesized via the so-called precursor sulfinyl route [34][35]. Next to a very fast polymerization and high conversion being reached within a second to minute time scale, this specific route differs from others in its use of an unsymmetrical premonomer which results in better control over the regioregularity as compared to for instance, the Gilch route 35. In addition to this, the sulfinyl precursor route enables the design of complex polar functionalized PPVs, as CPM-MDMO-PPV, in an easy manner.…”

Modifiable poly(p-phenylene vinylene) copolymers towards functional conjugated materials

“…36 Synthesis of 1-bromomethyl-2,5-dicyano-4-[(octylsulfinyl)methyl] benzene (13) Compound 10 was synthesized by means of a substitution reaction with CuCN on 9. 37,38 Crude product 10 could be purified via recrystallization in ethanol to obtain white needle-like crystals.…”