Well-Defined and Precision-Grafted Bottlebrush Polypentenamers from Variable Temperature ROMP and ATRP

Abstract

Polypentenamer macroinitiators are synthesized through variable temperature ring opening metathesis polymerization of 3-cyclopentenyl α-bromoisobutyrate, which has sufficient ring strain (ΔH p = −22.6 kJ mol −1 ) to produce targeted molar mass (<5% from theoretical), low dispersity (1.17 ≤ Đ ≤ 1.23), and high conversion (∼72%). An initiation site for atom-transfer radical polymerization at every fifth backbone carbon allows "grafting-from" of styrene with quantitative initiation and linear molar mass increase with time. These bottlebrushes retain a low dispersity (Đ ≤ 1.34) at varying graft degrees of polymerization (5 ≤ N sc ≤ 49) and have a glass transition temperature highly sensitized to graft length. Extension of the grafts with methyl methacrylate produces a core−shell brush polymer with high molar mass (>1000 kg mol −1 ) and Đ = 1.33. This system exhibits high synthetic versatility and control with a unique flexible backbone to expand the suite of densely grafted polymers.

Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

“…[ 48,57,64 ] The further realization that cyclopentene, functionalized cyclopentenes, and other five‐membered alkene rings can be ring‐opened through judicious selection of reaction conditions has spawned recent development of polypentenamer elastomers and related materials, including networks with continuous recyclability through sequential ring‐opening and ring‐closing metathesis. [ 65–72 ] Inspired by this general motif, we report here a series of novel PUs derived from carefully designed, unsaturated polyols, enabling facile depolymerization of the PUs by olefin metathesis.…”

Ring Opening Metathesis Polymerization of a New Monomer Derived from a Nitroso Diels–Alder Reaction

“…Polymers derived from the latter three contain functionality directly connected to the polymer backbone, which can have dramatic effects on physical properties like glass transition (T g ) temperatures. [11] Additionally, as is the case for polymers made with acyclic diene metathesis [12] polymerization, these materials can undergo subsequent hydrogenation to provide functionalized, precision "polyethylenes." [13][14][15][16][17][18] Similar materials can be prepared by polymerizing cyclopentene derivatives in which subsequent hydrogenation of the polypentenamer provides saturated, polyolefin analogues composed of precisely placed functionality.…”

“…[20] The same lab (and others) have shown that polymers can be prepared with precisely placed functionality along the carbon backbone with mono-functionalized cyclopentenes. [11,[21][22][23][24][25][26] However, preparing macromolecules from cyclopentenes functionalized at, both, the 1 and 3 positions seems to be less straightforward. Grubbs and co-workers showed the ROMP of 1,3-diol 1 (as well as its diester derivative 2) to be unsuccessful, due to the chelation to the metal center (Figure 1a).…”

Design, Synthesis, and Self‐Assembly of Janus Bottlebrush Polymers

“…[5][6][7] The initial synthesis of bottlebrush polymers was reported in the 1980s. [8,9] Until now, grafting-from (backbone-first), [10,11] grafting-to (backbone-first), [12,13] and grafting-through (side-chain-first) [14,15] approaches have been developed to prepare a series of bottlebrush polymers ( Figure 1A). According to the architecture, bottlebrush polymers are basically classified into homo-, [16,17] block-, [18,19] random-, core-shell-, [20,21] and Janus-types [22,23] ( Figure 1B).…”