Structure and Radical Mechanism of Formation of Copolymers of C₆₀ with Styrene and with Methyl Methacrylate

Abstract

Polymerizations in 1,2-dichlorobenzene solutions containing 0.33 volume fraction of styrene or methyl methacrylate (MMA) and relative weights of monomer/C 60/azo(bisisobutyronitrile) (AIBN) of 100:1.00:1.12 at 75 °C form high molecular weight materials in which all of the C60 is incorporated covalently. To understand the structures of the polymers and their mechanism of formation, samples were isolated after low conversion of monomer and analyzed. Molar size exclusion chromatograms from UV detection of fullerenes, differential refractive index detection of the mass of the polymer, and differential viscometry detection of the specific solution viscosity of the polymer show that the fullerene reacts rapidly, and both polystyrene/C 60 and PMMA/C60 products isolated after low conversion of monomer contain many fullerenes per molecule. Lower intrinsic viscosity and higher absolute molecular weight of the fullerene-containing polymers compared with linear polystyrenes at equal retention time show that the polymer structures are branched. Elemental analyses, NMR spectra, and size exclusion chromatograms show that the C 60 content is higher and the polymer chain lengths are shorter in the low-conversion polystyrene/C60 than in the low-conversion PMMA/C60. C60 itself polymerizes when initiated by AIBN. NMR analyses of polymers formed by initiation with AIBN-R-13 C show that in both polystyrene/C60 and PMMA/C60 at low conversion 62-72% of the 2-cyano-2-propyl groups are bound to polymer chain ends, and 28-38% are bound to fullerenes. Neither low molar mass AIBN/C60 adducts nor the polymers at any degree of conversion initiate further polymerization of monomer. Thus, the formation of 2-cyano-2-propyl to fullerene and polymer to fullerene carbon-carbon bonds is irreversible. After high conversion both polystyrene/C60 and PMMA/C60 contain much linear polymer. The average number of fullerene units per molecule decreases with increasing reaction time, and after complete reaction of monomer, all polystyrene/ C60 samples and some PMMA/C60 samples still have an average of more than one fullerene unit per macromolecule at the high end of the molecular weight distribution. Fullerene radicals were detected by ESR spectroscopy in all of the solid polymers recovered at low and high conversion. Evaluation of a radical chain mechanism for the copolymerizations using estimated rate constants for the microscopic steps shows that the fullerene must exist as clusters early in the polymerization, and that the clusters break down to macromolecules containing smaller numbers of fullerene units as the polymerization continues.

Polymers Grafted to Single‐walled Carbon Nanotubes by Radical Polymerization

“…C 60 reacts with polymer radicals at rate constants only one or two powers of ten slower than diffusion controlled. [9] Rate constants for addition of polymer radicals to SWCNT must be slower than to C 60 because SWCNT are less strained than C 60 , but still much faster than propagation of polymer radicals with carbon-carbon double bonds of monomers. It is well known from other polymer grafting investigations that the number of chains that can be grafted to a surface is smaller than the number of chains that can be grafted from the surface.…”

Lacunarity properties of nanophotonic materials based on poly(methyl methacrylate) for contact lenses

“…20 The easiest method of incorporation of C 60 into a polymer is radical copolymerization, which can produce materials of widely varied fullerene content, but the degree of substitution of the fullerene is hard to control, and the structures are heterogeneous and hard to determine. 21 The aforementioned nanomaterials were incorporated into the standard RGP SOLEKO TM material (Pontecorvo, Italy) known by the commercial name SP40 TM . This material belongs to the group of polymers known as poly-MMA-co-siloxy silane methacrylate, whose optical characteristics are given in Table 1.…”

Kinetics of Fullerene (C60) Inhibition in Polymerization of Vinyl Acetate (VA) Using Bismuthonium Ylide as Initiator

“…Fullerene (C 60 ), due to its unique properties [1,2], has applications in different fields such as pharmaceuticals [3], automobiles [4], preparation of fullerene-based polymers [5][6][7] and co-polymers [8][9][10]. Fullerene-containing polymeric materials have novel optical [11][12][13] and electro active properties [14][15][16][17][18] and have been used in organic solar cells [19,20].…”