Synthesis and Direct Topology Visualization of High-Molecular-Weight Star PMMA

Abstract

We report synthesis and direct topology visualization of single molecules of six-arm star poly(methyl methacrylate) (PMMA). We synthesized two hexafunctional initiators, 2,3,6,7,10,11-triphenylene hexa-2-bromo-2-methylpropionate (fused-core initiator) and ethylene glycol bis [3,4,5-tri(2-bromo-2-methylpropionate)] benzoylate (linear-core initiator). Their structures differ in the linking arrangement of the initiating sites. Atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) from these initiators using CuCl as the catalyst and 4,4′-di-n-nonyl-2,2′-bipyridine as the ligand at 90 °C produced six-arm star PMMAs with very high molecular weight (M h w> 2 million) and narrow molecular weight distribution (polydispersity index ≈ 1.3). A high initiation efficiency (>90%) of the initiating sites is inferred from a good match of the M h w of the star PMMA with the expected value based on M h w of the cleaved arms. SEC-LS analysis confirmed the compact structure of the star PMMA compared to linear PMMA and the absence of star-star coupling. Tapping mode scanning force microscopy of a dip-coated sample on mica enabled resolution of the individual arms linked to the initiating core and allowed clear identification of predominantly six-arm star molecules.

Chain Walking Ethylene Copolymerization with an ATRP Inimer for One‐Pot Synthesis of Hyperbranched Polyethylenes Tethered with ATRP Initiating Sites

“…However, a shoulder peak at the low-molecular-weight end was observed for all the polymer samples collected throughout the polymerizations, and its molecular weight and relative intensity increased with polymerization time, which indicates the occurrence of chain transfer at the given polymerization condition. [18,19] However, no shoulder peak is observed at the high-molecular-weight end, which suggests the absence of intermolecular chain coupling. Further research on ATRP using these macroinitiators will be carried out to improve the livingness of the polymerization system.…”

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

“…The literature on the results of such investigations is rather extensive and is thoroughly classified in several reviews, see, e.g., ref. [174][175][176] Other examples of synthetic structures being 'convenient' for visualisation with SFM include dendronised, [177,178] hyperbranched, [179][180][181] helical [126,127,[182][183][184] and some other [185][186][187] complex macromolecular structures. Some additional references on the relevant literature about SFM studies of similar objects may be found, e.g., in ref.…”

Synthesis of high molecular weight 3-arm star PMMA by ARGET ATRP

“…These results indicate that the ARGET ATRP of MMA has controlled/living characteristics. Xue et al 10 synthesized high MW 6-arm star PMMA (M n =~1,010,000 g/mol, PDI = ~1.30) using a hexafunctional initiator via ATRP at 90 o C. However, this MW was determined after the removal of the linear PMMA chains formed by chain transfer reactions during the ATRP process.…”