Complex Brush‐Like Macromolecular Architectures via Anionic and Ring Opening Metathesis Polymerization: Synthesis, Characterization, and Thermal Properties

Abstract

Combination of anionic and ring opening metathesis (ROMP) polymerizations is conducted for the synthesis of different series of brush polymers adopting the macromonomer methodology. Specifically, poly(tert‐butoxystyrene) (PtBOS), polystyrene (PS), and poly(ethylene oxide) (PEO) macromonomers, having end norbornene groups, are prepared by anionic polymerization techniques and suitable termination reactions or functional anionic initiators. These macromonomers are either homopolymerized or copolymerized by ROMP employing Ruthenium Grubbs catalysts of the 1st or 3rd generation leading to the formation of polymer brushes. Using this synthetic approach, PtBOS polymacromonomers, PtBOS‐PEO block and random copolymacromonomers, and PtBOS‐PS random copolymacromonomers are prepared. Acidic hydrolysis of the tert‐butoxy groups of the PtBOS brushes affords the corresponding polyhydroxystyrene (PSOH) brushes. Subsequent activation of the hydroxyl groups upon reaction with triphenylmethyl potassium and addition of ethylene oxide lead to the formation of PEO brushes on the PSOH brushes (brush on brush structures). These materials are thoroughly characterized by size exclusion chromatography, and 1H‐NMR spectroscopy. The thermal properties are studied by differential scanning calorimetry, thermogravimetric analysis , and differential thermogravimetry.

OH‐ and NH2‐Terminated Hyperbranched Polysiloxanes: Controlled Synthesis, Characterization, Toughening, and Reinforcing Epoxy Resin

“…Jin used amine‐terminated hyperbranched polyimide (HBPI) to toughen E51/DDM curing systems, finding that good compatibility with epoxy networks can simultaneously improve toughness and T g . However, in these works, hyperbranched modifiers suffer from tediousness stepwise and higher cost, leading to difficulty in a large scale industrial application . In fact, a lot of papers are available in the literature, which describes the various synthetic approaches for the preparation of HBPSi using catalytic hydrosilylation, esterification, hydrolysis of siloxanes, reversible‐deactivation radical polymerization (RDRP), and proton transfer reactions (PTR) .…”

Grubbs’ and Schrock’s Catalysts, Ring Opening Metathesis Polymerization and Molecular Brushes—Synthesis, Characterization, Properties and Applications

“…PEO molecular brushes have been incorporated in more complex architectures ( Figure 4 ) due to the living character of Grubbs’ catalysts. Copolymers with polylactides [ 56 , 57 , 58 ], polystyrene and polystyrene derivatives [ 8 , 27 , 47 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 ], ε-caprolactone [ 52 , 53 ], (meth)acrylates [ 70 , 71 , 72 , 73 ], peptides [ 35 , 74 , 75 , 76 , 77 ] have been synthesized and studied. The covalent attachment of drug molecules on the PEO side chains or as a separate block on the main chain has also been employed for drug delivery purposes [ 78 , 79 , 80 , 81 , 82 , 83 , 84 ].…”

“…Block molecular brushes ( Figure 4 A) that have been reported in the literature are: (a) diblocks PS- b -PEO [ 8 , 27 , 62 , 63 , 64 , 65 , 66 ], PEO- b -P t BOS [ 68 ], PEO- b -(poly)peptide [ 75 , 76 , 77 ], P t BA- b -PEO [ 70 , 71 ], and (b) triblocks PEO- b -PDLLA- b -PBAEAM [ 57 ], PS- b -PEO- b -PS [ 61 ]. Molecular brushes with random side chains ( Figure 4 B) have been synthesized: PS- co -PEO [ 27 , 59 ], PEO- co -PCL [ 52 ], PE- co -PCL- co -PEO and PE- co -PCL- co -PEO- co -PS [ 47 ], P t BOS- co -PEO [ 68 ] and random copolymers of PEO with three different end groups [ 97 ]. Bottlebrushes with two PEO chains per monomeric unit ( Figure 4 C) have been prepared [ 52 ].…”

“…Similar structures without drugs have been synthesized with PEO (and/or PS) brush arms recently [ 67 , 101 ]. A brush on brush advanced structure, where polymeric chains have been grown from initiation sites on the bottlebrush side chains, has been reported in 2018 [ 68 ].…”

“…The last paper where “graft from” was used for PS was published in 2011 [ 108 ]. PS macromonomers have been employed by other teams (Hadjichristidis, Pitsikalis) in copolymer synthesis with G1 and no significant problems were mentioned [ 47 , 68 ]. Ultra-high molecular weight PS bottlebrushes have been synthesized using G3’ [ 69 ] .…”