Michael D. Schulz

Aminobisphosphonate Polymers via RAFT and a Multicomponent Kabachnik–Fields Reaction

Polyacrylamides containing pendant aminobisphosphonate groups are synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and a multicomponent postpolymerization functionalization reaction. A Moedritzer-Irani reaction installs the phosphonic acid groups on well-defined, RAFT-generated polymers bearing a pendant amine. An alternate route to the same materials is developed utilizing a three-component Kabachnik-Fields reaction and subsequent dealkylation. Kinetics of the RAFT polymerization of the polymer precursor are studied. Successful functionalization is demonstrated by NMR and FTIR spectroscopy and elemental analysis of the final polymers.

Acyclic diene metathesis polymerization and precision polymers

The history of and major advances in the acyclic diene metathesis (ADMET) reaction are described. Because precise branch identity and frequency can be achieved by ADMET polymerizations of symmetrical α,ω-dienes, polyethylenes with precisely spaced alkyl branches of specified length have been prepared. Investigations of their morphologies and thermal properties have provided valuable insight into the behavior of polyethylene. ADMET preparation of ethylene copolymers and telechelic oligomers, as well as the properties of these materials, is also discussed.

Insertion metathesis depolymerization

We have successfully depolymerized polybutadiene via an insertion metathesis mechanism. This new concept involves the irreversible depolymerization of unsaturated polymers with electron deficient olefins. The product of the degradation was characterized by NMR and GC-MS. We also explored the use of copper iodide as an additive. We observed significant reduction of molecular weight under a variety of conditions with the most extensive depolymerization occurring with the use of Grubbs 2nd generation catalyst with CuI. Finally, polybutadiene was converted to a polyamide by performing insertion metathesis depolymerization with acryloyl chloride and subsequently reacting with 1,6-diaminohexane, demonstrating the potential of polymer-to-polymer conversions with this chemistry.

Functionalized 3D Architected Materials via Thiol-Michael Addition and Two-Photon Lithography

Fabrication of functionalized 3D architected materials is achieved by a facile method using functionalized acrylates synthesized via thiol-Michael addition, which are then polymerized using two-photon lithography. A wide variety of functional groups can be attached, from Boc-protected amines to fluoroalkanes. Modification of surface wetting properties and conjugation with fluorescent tags are demonstrated to highlight the potential applications of this technique.

Morphology control in precision polyolefins

Herein, we review the major advances in controlling polyethylene morphology through precise control of branch frequency and identity. This control is made possible by the acyclic diene metathesis reaction.

Modular segmented hyperbranched copolymers

Modular segmented hyperbranched polymers, amenable to facile post-polymerization functionalization, were created via two distinct approaches. Self-condensing vinyl polymerization via reversible addition–fragmentation chain transfer (RAFT) polymerization and RAFT polymerization with a divinyl comonomer were employed to create well-defined highly branched materials containing activated esters amenable to highly efficient functionalization in a modular manner.

Copper(I) halides inhibit olefin isomerized by-products from phosphine-based Grubbs' metathesis catalysts in polar protic solvents

Copper(I) halides are employed as ‘phosphine sponges’ to sequester phosphor-ylides when using phosphine-based Grubb’s metathesis catalysis in polar protic solvents and under heat. These cuprous halides are hypothesized to significantly slow the formation of the ruthenium hydride olefin isomerization catalyst. We demonstrate their use in both cross metathesis and ring-closing metathesis.Graphical Abstract

Application of Ionic Liquids in Pot-in-Pot Reactions

Pot-in-pot reactions are designed such that two reaction media (solvents, catalysts and reagents) are isolated from each other by a polymeric membrane similar to matryoshka dolls (Russian nesting dolls). The first reaction is allowed to progress to completion before triggering the second reaction in which all necessary solvents, reactants, or catalysts are placed except for the starting reagent for the target reaction. With the appropriate trigger, in most cases unidirectional flux, the product of the first reaction is introduced to the second medium allowing a second transformation in the same glass reaction pot—albeit separated by a polymeric membrane. The basis of these reaction systems is the controlled selective flux of one reagent over the other components of the first reaction while maintaining steady-state catalyst concentration in the first “pot”. The use of ionic liquids as tools to control chemical potential across the polymeric membranes making the first pot is discussed based on standard diffusion models—Fickian and Payne’s models. Besides chemical potential, use of ionic liquids as delivery agent for a small amount of a solvent that slightly swells the polymeric membrane, hence increasing flux, is highlighted. This review highlights the critical role ionic liquids play in site-isolation of multiple catalyzed reactions in a standard pot-in-pot reaction.