Nitroxide‐mediated radical polymerization of methacryloisobutyl POSS and its block copolymers with poly(n‐acryloylmorpholine)

Abstract

Nitroxide-mediated radical polymerization (NMP) of the bulky methacryloisobutyl-polyhedral oligomeric silsesquioxane (POSS-MA) is successfully achieved after optimizing reaction conditions such as selection of controlling comonomer, comonomer feed molar ratio, and temperature (10 mol % styrene (S) comonomer at 110 C using the commercially available BlocBuilder as the NMP initiator). The P(POSS-MA-co-S) with a molecular weight of~8000 g/ mol and dispersity Ð-1.2 is afforded under the optimized reaction conditions. The chain-end fidelity is verified by chain extension experiments with N-acryloyl morpholine (ACM) via NMP that produces well-defined amphiphilic hybrid P(POSS-MA-co-S)-b-P(ACM) x block copolymers, where the subscript "x" represents the degree of polymerization of (ACM) block (182 < x < 695). The size exclusion chromatography (SEC) of the as-synthesized samples reveals the presence of some dead P(POSS-MA-co-S) chains that could be removed by a simple purification step. Kinetic investigations reveal a first-order kinetics for the polymerization of ACM using P(POSS-MA-co-S) as the macroinitiator under NMP conditions. The kinetic and SEC data confirms the controlled nature of the NMP of ACM. Being amphiphilic, the formed P(POSS-MA-co-S)-b-P(ACM) x block copolymers self-assembled in aqueous solution as revealed by the fluorescence spectroscopy experiments with pyrene as the probe for determination of the critical micelle concentration and dynamic light scattering studies.

Properties and molecular self‐assembly of liquid crystalline hard–hard diblock and hard–soft–hard triblock copolymers influenced by Flory–Huggins interaction parameter and volume fraction of distinct segments

“…Polyethylene, polyacrylonitrile, polystyrene, poly( n ‐alkyl methacrylates) and azobenzene‐containing poly(meth)acrylates used typically as hard blocks while poly(ethylene glycol), poly(tetramethylene glycol), poly(dimethylsiloxane), polyisoprene, polybutadiene, poly(methyl acrylate), and poly(methyl methacrylate) utilized as soft blocks 38,40,66,70,77 . Generally, BCs based on hard and soft blocks are prepared by the three most commonly used methods including nitroxide‐mediated polymerization (NMP), 78,79 atom transfer racial polymerization (ATRP) 80,81 and reversible addition‐fragmentation chain transfer (RAFT) 82,83 to control their molecular weight, dispersity ( M w /M n = Đ), composition and chain architecture. The RAFT technique has recently become an almost universal synthetic strategy for producing BCs having predetermined molecular weight and very narrow dispersity because of its compatibility with various reaction conditions, its good tolerance to a wide range of functional groups and its broad applicability to most vinyl monomers when compared with the NMP and ATRP 79,84–86 …”

“…The RAFT technique has recently become an almost universal synthetic strategy for producing BCs having predetermined molecular weight and very narrow dispersity because of its compatibility with various reaction conditions, its good tolerance to a wide range of functional groups and its broad applicability to most vinyl monomers when compared with the NMP and ATRP. 79,[84][85][86] Herein, this article describes the molecular design, synthesis and study of the structural and thermal properties as well as the self-assembly behavior of two series of linear hybrid AB-type hard-hard diblock copolymers (DBCs) and ABC-type hard-soft-hard triblock copolymers (TBCs) with well-defined molecular weights, dispersities, architectures, and compositions. Both BC series were obtained by typical RAFT polymerization using azobisisobutyronitrile (AIBN) as a radical initiator and anisole as a solvent.…”

Nitroxide mediated miniemulsion polymerization of methacryloisobutyl POSS: Homopolymers and copolymers with alkyl methacrylates

“…Methacrylic POSS contain one or more methacrylic ligands, which enables free radical polymerization. Many studies have illustrated the successful radical polymerization (conventional, [ 17,18 ] atom transfer radical polymerization [ATRP], [ 19–21 ] reversible addition‐fragmentation chain transfer [RAFT] [ 22,23 ] and nitroxide mediated polymerization [NMP] [ 24,25 ] ) of methacrylic POSS. One of the methacrylic POSS compounds is 3‐(3,5,7,9,11,13,15‐heptaisobutylpentacyclo [9.5.1.…”

“…POSSMA‐rich copolymers with 10 mol% acrylonitrile (AN) or styrene (S) in the initial monomer mixture was previously synthesized in our research group using N‐(2‐methylpropyl)‐N‐(1‐(diethylphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2yl)hydroxylamine) BlocBuilder‐MA (BB, Arkema). [ 24,25 ] Charleux et al [ 28 ] showed that the polymerization of methacrylate‐rich compositions (essentially mimicking homopolymerization) by BB alkoxyamine was feasible using a low concentration of controlling comonomer with a very low activation/deactivation equilibrium constant such as AN or S, which was thought to decrease the average equilibrium constant for activation/deactivation of the chains 〈 K 〉 and to also reduce cross‐disproportionation side reactions. [ 29–31 ]…”

Incorporation of methacryloisobutyl POSS in bio‐based copolymers by nitroxide mediated polymerization in organic solution and miniemulsion

“…4,6,8 Methacryloisobutyl POSS (termed herein as POSSMA) is a POSS containing molecules (n = 8) with one methacrylic ligand, which can be incorporated into polymer resins to improve the hardness (T g of poly(POSSMA) ≈ 85 C) 9 and thermal stability. The reversible-deactivation radical polymerization (RDRP) of POSSMA with different monomers was previously studied in organic solvents [10][11][12][13][14][15][16][17] and reported in dispersed aqueous media recently. 18 Nitroxide mediated polymerization (NMP), as one of the simplest RDRP techniques, can be used to prepare POSSMA-containing polymers with active chain ends, well-defined microstructures and narrow molecular weight distributions.…”