Precision Polymers through ADMET Polymerization

Abstract

Acyclic diene metathesis (ADMET) polymerization is a unique strategy for achieving polymers with precise control over the primary structure. This precision is obtained by specifi c monomer design and carefully controlled polymerization conditions. Over time, this approach has produced an array of sophisticated architectures ranging from precise polyethylenes, to hyperbranched polymers, to rotaxanes.ADMET polymerization (Figure 1 ) comprises an α,ω-diene monomer and a suitable olefi n metathesis catalyst. Typically the metathesis precatalyst is activated by the initial reaction with the diene monomer, yielding a metal alkylidene species, which subsequently reacts with another diene, releasing the newly formed dimer and the metal methylidene species. The metal methylidene is generally regarded as the true catalytic species in the reaction. Subsequent reactions with monomer or polymer produce ethylene, which is typically removed under high vacuum conditions. The removal of ethylene drives the reaction toward polymer formation due to the equilibrium nature of the polymerization. [ 2 ] The history of ADMET's discovery has been detailed elsewhere, [ 3,4 ] but it is important to point out that the development of ADMET polymerization is the direct result of breakthroughs in olefi n metathesis catalysis by Schrock [5][6][7][8][9][10] and Grubbs. [11][12][13][14][15][16][17] Without the creation of effective olefi n metathesis catalysts (Figure 2 ), effi cient ADMET polymerization would not be possible. Here we review the development of "precision polyolefi ns," and the most recent advances in ADMET chemistry. Precision Polyolefi nsConventional ADMET polymerization results in an allhydrocarbon backbone. Consequently, it is a useful method of synthesizing polymers that model commercially

A Precision Ethylene‐Styrene Copolymer with High Styrene Content from Ring‐Opening Metathesis Polymerization of 4‐Phenylcyclopentene

“…An alternative strategy to ethylene copolymers is ring‐opening metathesis polymerization (ROMP) of strained monocyclic alkenes or acyclic diene metathesis (ADMET) polymerization of linear dienes followed by hydrogenation of the backbone olefins. In both cases a singular monomer can be used to impart periodic chain branching with functionalities that are analogous to copolymer systems.…”

“…In both cases a singular monomer can be used to impart periodic chain branching with functionalities that are analogous to copolymer systems. Precision polymers are a subset of these materials that incorporate branches at perfectly spaced periodicity along a polyethylene chain . The regiospecific branching of these systems leads to well‐defined properties for specialty applications .…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…(10) preparation of stereoregular polymers via ROMP [37]; (11) preparation of self-assembled supramolecular polymers [38]; (12) combining ROMP and thiol-ene coupling chemistry for preparation of linear and nonlinear macromolecules [39]; (13) synthesis of cyclo-polyolefins through ring expanding metathesis polymerization [40]; (14) precision polymers through ADMET polymerization [41,42]; (15) systematic studies of morphological changes of ADMET-derived precision polyethylene [43]; (16) concurrent cross metathesis and enzymatic oxidation reactions [44]; (17) rhenium oxide based olefin metathesis [45]; and (18) olefin metathesis over molybdenum-exchanged zeolites [46]. Additional reviews in languages other than English include: (1) olefin metathesis in complex synthesis [47]; (2) Z-selective olefin metathesis catalysts and their applications [48]; (3) modification of biodiesel using olefin metathesis [49]; (4) cyclic aminocarbene complexes (Bertrand carbene complexes) in olefin metathesis reactions [50]: (5) progress in ROMP of dicyclopentadiene [51]; and (6) the role MgO in WO 3 / SiO 2 catalyzed olefin metathesis [52].…”

Synthesis of supramolecular precision polymers: Crystallization under conformational constraints

“…Famous examples for the latter case are block copolymers, where glassy or crystalline matrices influence the crystallization of crystallizable domains with typical domain sizes of about 10–50 nm, or nanophase separated polymers with comb‐like architecture, where constraints introduced by ring‐type subunits located in a crystalline nanolayer can disturb the crystallization behavior of long methylene sequences . In case of linear polymers, where long methylene sequences alternate with functional groups (“defects”) within the polymer backbone, their incorporation or exclusion into crystalline regions has been intensively studied . Especially precision polymers, resulting from acyclic diene metathesis (ADMET) polymerization or “click”‐based oligomerization chemistries, have been investigated in this context, often observing a layered arrangement of defects if the included moieties interact with each other via ionic‐forces or π–π‐stacking as observed for polymers bearing triazol‐rings, sulfonic, or amino acid groups in the main chain .…”