Reactivity in Radical Polymerization of Poly(2-oxazoline) Macromonomers

Abstract

ABSTRACT:Reactivity in radical homopolymerization of vinylbenzyl-ended poly(2-alkyl-2-oxazoline) macromonomers (VB-PROZO-n; n (degree of polymerization)=3-34) and methacryloyl-ended macromonomcrs (MA-PROZO-n; n=4-34) was examined at 60°C in CD 3 CN, CDCI3 , or D 2 0 using 2,2'-azobis(isobutyronitrile) (in organic solvents) or 2,2'-azobis(2-amidinopropane) dihydrochloride (in D 20) as initiator. R was Me, Bu, or n-octyl (Oc) group. In CD3CN (R=Me, Bu), macromonomers were polymerized faster with increase in n. Higher RP was observed for Bu group and MA end group than Me group or VB end group, respectively. In CDCI3 , polymerization of VB-ended POcOZO macromonomers showed higher RP than PBuOZO macromonomers. The rate increased with in n, whereas, polymerization of MA-ended POcOZO macromonomers showed lower Rp than PBuOZO macromonomers of similar n, and rate decreased with increase in n. In D 2 0, PMeOZO macromonomers were polymerized 9 to 14 times faster than CD3CN. Kinetic orders of monomer concentration were 1.55 to 1.73 in organic solvents, while nearly 1.0 in water, and those of initiator concentration were close to 0.5 in CD3CN. RP is thus affected by carbon number of acyl side chains in PROZO and by n, and D 20 increases enormously RP of PMeOZO macromonomers by micelle formation.KEY WORDS Macromonomers I Polyoxazoline I Radical Polymerization I Kinetics I Reactivity I Cationic ring-opening polymerization of 2-alkyl-2-oxazoline (ROZO) gives poly(2-alkyl-2-oxazoline) (PRO-ZO) having poly(N-acylethylenimine) structure. PROZO can be regarded as a polymer homologue of polar aprotic solvents such as N,N-dimethylacetamide, exhibiting hydrophilic (R= Me, Et) or hydrophobic (carbon number of R 2 4) properties. 1 Macromonomers of PROZO, e.g., styryl-2 , methacryloyJ-3, and vinylester-terminated 4 macromonomers have been synthesized using living polymerization of ROZO.Macromonomers possess large importance and potential as building block for functional polymeric materials. Copolymerization with small-sized monomers produces graft copolymers with well-defined structure, and homopolymerization forms star-like or comb-like polymers. In contrast to polymerization of small monomers, polymerization systems of macromonomers have the following characteristics; (I) propagation reactions are polymer-polymer reactions, (2) concentrations ofpolymerizable end groups are low, (3) viscosity of polymerization systems is high from the initial stage of the reaction,5 and (4) segment density around the propagating species is high. 5 These factors (1)-(4) have been found to affect greatly polymerization rates and molecular weights of poly(macromonomer)s. Sab.6 Radical copolymerizations of PROZO macromonomers produce micron or submicron-size polymer particles utilizing macromonomers as stabilizer or emulsifier, 7 and form amphiphilic polymers from hydrophilic macromonomers and hydrophobic small monomers, i.e., styrene and methyl methacrylate (MMA). 8 It is essential to know the characteristics of macromonomer reactivity in polymerization t...

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.…”

“…8,[18][19][20] Furthermore, multiple functionalization and structural versatility are possible using respective initiators, monomers and terminating agents. 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. The majority of the applied methods focuses on the polymerization of macromonomers by group transfer polymerization(GTP), free radical polymerization (FRP) or reversible addition/fragmentation chain transfer polymerization (RAFT).…”

Cationic Bottlebrush Copolymers from Partially Hydrolyzed Poly(oxazoline)s

“…Styryl macromonomers provide an effective route toward nondegradable architectures. In addition, there have been several reports on their synthesis and subsequent polymerization, ,, with Störkle et al reporting the hydrolysis to form bottlebrush poly­(ethylenimine) . In this initial study, the bottlebrush polymers were synthesized by free radical polymerization, offering no control over the bottlebrush molecular weight, and the hydrolysis was uncontrolled leading to fully hydrolyzed materials.…”

“…In addition, the choice of monomer can provide a functional handle for attaching grafts or imparting properties such as biocompatibility or thermo-responsiveness . A wide variety of different POx-based macromonomers have been reported in the literature, including (meth)­acrylate, − styryl, ,− diene, and cyclic alkenes such as norbornene and pyrrole macromonomers. Functional end-groups or the active chain end of the polymerization are also readily accessible, allowing for grafting-to reactions to be undertaken .…”

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

“…The reactivity was strongly affected by carbon number of the alkyl groups and by PROZO chain length. 4 Reactivity in radical copolymerization of vinylbenzylterminated PROZO macromonomers with ordinary vinyl monomers was studied. 5 H20, Na2C03 1 To whom correspondence should be addressed.…”