Reactivity in the Radical Copolymerization of Poly(2-oxazoline) Macromonomers with Methacrylate Monomers

Abstract

ABSTRACT:The radical copolymerization ofvinylbenzyl-terminated poly(2-methyl-2-oxazoline) macromonomers (I Me-n; n (degree of polymerization)=3, 15, 28, 31) (M 1 ) with vinyl monomers (M 2 ), i.e., methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) was performed using 2, 2'-azobis(isobutyronitrile) (AIBN) as an initiator at 60"C in ethanol (EtOH), CD 3 0D, or CD 3 CN. Monomer reactivity ratios r1 and r2 were evaluated based on the terminal model. Copolymerization oft Me-3 with MMA gave reactivity ratios as r 1 = 1.86 ±0.15 and r2 =0.07 ±0.03 in EtOH, and r1 = 1.25 ±0.10 and r 2 =0.18±0.05 in CD 3 0D. exhibiting remarkably higher reactivity of the Me-3 compared with the comonomers and corresponding small monomer, styrene. In CD3CN, however, copolymerization of I Me-3 with MMA gave r 1 =0.41 ±0.10 and r 2 = 0.66 ± 0.1 0, showing rather lower reactivity of the macromonomer compared with MMA. With HEMA, I Me-3 showed high reactivity in EtOH, i.e., r 1 = 1.44± 0.10, r2 =0.04 ±0.02. The reactivity of HEMA against the macromonomers was found higher than that of MMA, possibly due to affinity to aprotic poly(2-methyl-2-oxazoline) graft chains on growing species. The high reactivity of I Me-n in EtOH and CD30D would be due to the formation of a micelle-like state. The reactivity of macromonomers decreased generally with chain length (n).KEY WORDSPoly(2-alkyl-2-oxazoline)s (PROZO) having the poly-(N-acylethylenimine) structure given by cationic ringopening polymerization of 2-alkyl-2-oxazoline (ROZO), can be regarded as a polymer homologue of polar a protic solvents such as N,N-dimethylacet-amide, showing hydrophilic (R =Me, Et) or hydrophobic (carbon number of R 2: 4) properties. 1 Monodisperse macromonomers ofPROZO, e.g., styryl-, 2 methacryloyl-, 3 and vinylester-terminated4 macromonomers, have been synthesized using living polymerization of ROZO. Longer alkyl groups (R) in PROZO chain make macromonomers with regularly branched structure.In general, homopolymerization of macromonomers produces star-like or comb-like polymers, while copolymerization with ordinary vinyl monomers forms graft copolymers. In particular, the synthesis of graft copolymers using the macromonomer method is believed very good for those with well-defined structure. We examined the kinetics of radical homopolymerization of methacryloyl and vinylbenzyl-terminated PROZO macromonomers, and found reactivity to be particularly influenced by longer alkyl (R) branches and remarkably enhanced in water. 5 Previously, radical copolymerization of hydrophilic PROZO macromonomers was found to produce micron to submicron-size polymer particles using the functions of macromonomers as stabilizers or emulsifiers. 6 Amphiphilic graft copolymers were obtained by copolymerization of hydrophilic PROZO macromonomers with hydrophobic monomers. 7 The reactivity of PROZO macromonomers in copolymerizations is of interest, though detailed examination on copolymerizability has not been reported.In the present study, reactivity of radical copolymerization of p-vi...

Preparation of highly branched polyethylene using (α‐diimine) nickel complex covalently supported on modified SiO2

“…As it has been reported in several studies on the copolymerization behavior of monofunctional macromonomers, in addition to the reactivity ratios of the comonomer units, that is, that of the low molecular weight counterpart of the terminal polymerizable group of the macromonomer and the other comonomer, several other factors, such as overall concentration, viscosity of the reaction medium and molecular weight of the macromonomer influence its apparent reactivity, and thus the structure of the resulting graft copolymers 39–44. It has been found that increasing the molecular weight of monofunctional macromonomers decreases their apparent reactivity in copolymerizations in most of the cases,29–39 and only few cases have been reported with unchanged40, 41 or increased42 reactivities with increasing molecular weights. As conetwork formation with telechelic macromonomers and the composition of the resulting conetworks are expected to depend strongly on the reactivity of the telechelic macromonomers, the effect of their molecular weight in this process is of paramount importance.…”

“…Monofunctional macromonomers with one terminal polymerizable group are frequently used to prepare graft copolymers via copolymerization with low molecular weight monomers (see e.g., refs 28–44. and references therein).…”

Poly(2-oxazoline) molecular brushes by grafting through of poly(2-oxazoline)methacrylates with aqueous ATRP

“…5,6 Molecular brushes based on poly(2-oxazoline)s (POx) got in focus of recent research because of the advantageous properties of POx as a biomaterial. 7,[21][22][23][24][25][26][27][28][29][30] After early approaches 31,32 yielding a variety of POx-based comb polymers, [33][34][35][36][37][38][39][40][41][42][43][44][45][46] POx molecular brushes have been synthesized recently by several routes. 7,8 Similar to poly(ethylene glycol) (PEG), hydrophilic POx is non-toxic, 9,10 non-immunogenic (low to none complement activation), 10,11 suppresses biofouling, 12,13 POxylated entities display the same "stealth effect" as PEGylated ones, [14][15][16] and hydrophilic as well as amphiphilic POx shows a biodistribution and excretion which is beneficial for medical applications.…”

Group Transfer Polymerization of Methacryl-Type Poly(2-oxazoline) Macromonomers

“…No. 5,1999 Polymerization rate at 50 C was generally higher than that at 24 C. Induction period was observed in a polymerization of MA-PBuOZ0-14 at 24 C. The retardation of polymerization at 24GC seems due to depression of initiation step. In GTP of methyl methacrylate with MTS, the induction period has been observed and interpreted in terms of slow initiation.…”

“…31, No. 5,1999 detected. M" of the products (6) (12600 and 13500) were reasonably higher than those (8200 and 10700) of 4, showing formation of block copolymers.…”