Synthesis and Characterization of Diblock and Gel-Forming Pentablock Copolymers of Tertiary Amine Methacrylates, Poly(ethylene glycol), and Poly(propylene glycol)

Abstract

Novel pH-sensitive gel-forming pentablock copolymers based on commercially available Pluronic (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), PEO-b-PPO-b-PEO) triblock copolymers and cationic diblock copolymers based on polyethylene glycol) methyl ether (PEGME) were synthesized by oxyanionic polymerization. Polymerization of the cationic moiety, poly((diethylamino)-ethyl methacrylate), PDEAEM, was initiated by a difunctional potassium alcoholate of the triblock Pluronic copolymer F127 (PEO106-PPO69-PEO106) or PEGME. The difunctionality of the initiation using the triblock macroinitiator, indicating formation of a pentablock copolymer rather than a tetrablock copolymer, was verified by functionalized termination of the living polymer chains. Critical micellization temperatures (cmt) of the synthesized polymers were obtained from differential scanning calorimetry for the pentablock materials. The pentablock copolymers retained the thermoreversible gel-forming properties of Pluronic F127 as well as similar cmt values. The polydispersity of both the diblock and pentablock copolymers was similar to the macroinitiators, indicating a very low polydispersity associated with the addition of the cationic PDEAEM blocks. Both of the materials show pH-sensitive release behavior, whereas the native polymers do not. ABSTRACT: Novel pH-sensitive gel-forming pentablock copolymers based on commercially available Pluronic (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), PEO-b-PPO-b-PEO) triblock copolymers and cationic diblock copolymers based on poly(ethylene glycol) methyl ether (PEGME) were synthesized by oxyanionic polymerization. Polymerization of the cationic moiety, poly((diethylamino)-ethyl methacrylate), PDEAEM, was initiated by a difunctional potassium alcoholate of the triblock Pluronic copolymer F127 (PEO 106-PPO69-PEO106) or PEGME. The difunctionality of the initiation using the triblock macroinitiator, indicating formation of a pentablock copolymer rather than a tetrablock copolymer, was verified by functionalized termination of the living polymer chains. Critical micellization temperatures (cmt) of the synthesized polymers were obtained from differential scanning calorimetry for the pentablock materials. The pentablock copolymers retained the thermoreversible gel-forming properties of Pluronic F127 as well as similar cmt values. The polydispersity of both the diblock and pentablock copolymers was similar to the macroinitiators, indicating a very low polydispersity associated with the addition of the cationic PDEAEM blocks. Both of the materials show pH-sensitive release behavior, whereas the native polymers do not.

Smart polymeric gels: Redefining the limits of biomedical devices

“…The ability to tune the stimuli responsive properties of block copolymers by modifying the architecture of the individual blocks as well as by incorporating blocks supplementing the properties of the parent block(s), have made the evolution process of novel block copolymers increasingly exciting. Along these lines, Mallapragada et al have conferred pH-sensitivity to Pluronic-based triblock copolymers by flanking on either side of the PF127 triblock, cationic moieties consisting of poly(diethylaminoethyl methacrylate) (PDEAM), a methyl ether of poly(ethylene glycol) with pendant amines [210]. At physiological temperature and pH values, aqueous solutions of this novel block copolymer coalesced to form phaseseparated hydrogels, stemming from the increasing hydrophobicity of the cationic PDEAM blocks at higher pH values (pK a value of the pendant amines of PDEAM = 7.6).…”

Effect of block composition on thermal properties and melt viscosity of poly[2-(dimethylamino)ethyl methacrylate], poly(ethylene oxide) and poly(propylene oxide) block co-polymers

“…In this study the initiation from KH was determined adequate for the polymerization. An excess of KH was used to eliminate possible termination reactions caused by residual OH groups [20].…”

“…This alcoholate synthesis was first introduced by Nagasaki et al [11], and later it was called oxyanionic synthesis when further studies of the mechanism were done [12,13]. Since then, numerous macroinitiators containing hydroxyl groups have been studied, among them PEO [14], PPO [15], poly(dimethyl siloxane) [16], short aliphatic carbon chains [17] and different combinations of these [14][15][16][17][18][19][20]. The oxyanionic method has also been successfully applied to polymerize some other methacrylates, like 2-(trialkylsiloxyethyl) methacrylate [21].…”

Phases of polymer systems in solution studied via molecular dynamics

“…This initial study is motivated by experiments performed by Prof. Mallapragada's group [8][9][10] which are aimed at developing polymer-inorganic composite materials. Studying such complicated systems with MD first requires a good understanding of the simpler case of just multiblock polymers in solution, a problem that was still poorly understood at the time [11].…”

“…This A15 lattice is characteristic of a minimal area tiling of the three dimensional space [39], and it has recently been predicted [40] to be a stable phase in melts of branched copolymers. Another example of polymer synthesis is the attachment of 2-(diethylamino)ethyl methacrylate (DEAEM) blocks to the ends of a Pluronic R F127 polymer [8]. DEAEM blocks are hydrophobic at high pH (pH ≥ 8), but as the pH is lowered the DEAEM groups gain a proton, become charged and therefore hydrophilic [41].…”