Seminar Series

Advanced Polymer Nanoparticles from Ring Opening Metathesis Polymerization (ROMP) in Water

Chunyang Zhu ABSTRACT Polymer nanoparticles are well known for their large volume applications such as coatings, paints, adhesives, and sealants. But current state-of-the-art technology including radical-initiated emulsion polymerization only works with a limited number of monomers like styrene and acrylates. Meanwhile, ring opening metathesis polymerization (ROMP) has been applied to prepare a range of high-value functionalized polymers which have unique backbones and properties, but this method only works with volatile organic solvents. Here we combine both techniques via developing an emulsion or miniemulsion polymerization process based on ring opening metathesis polymerization (ROMP) in order to synthesize well-defined polymer nanoparticles (latexes) in aqueous dispersions. Our approach focuses on the modification of ROMP catalyst which is typically employed in organic solvents; and the introduction of N-heterocyclic carbenes (NHCs) to the structure of catalyst suggests that the modified catalyst is more stable and tolerant in water phase. ROMP-based polymers including functionalized polynorbornene(PNB) and polycyclooctadiene (PCOD) can also be obtained by using optimized catalysts. Thus it is believed that our approach will achieve three important objectives: (1) enable the preparation of nanoparticles via ROMP method, which is currently impossible; (2) eliminate the use of large amount of volatile organic compounds (VOCs); and (3) dramatically improve the efficiency and lower the cost of manufacturing process.

Seminar Series

Chemical Modification of Alginate for Controlled Drug Delivery Vitaliy Kapishon

ABSTRACT Amphiphilic polymers have been widely used in encapsulation and delivery of hydrophobic drugs due to their ability to self-assemble in aqueous solution into micelles, polymersomes, vesicles, nanotubes, etc. An amphiphilic polymer has distinctive water soluble and water insoluble regions in a molecule. Alginate, a naturally found electrolyte polysaccharide, was chosen to be a hydrophilic block due to its biocompatibility. Less water soluble or hydrophobic polymers were synthesized using single electron transfer living radical polymerization (SET-LRP). Alginate was partially degraded to produce low molecular weight fragments (10-20 kDa) and modified to be soluble in organic solvents (DMSO, DMF) for further reactions. Alginate macroinitiator was synthesized with degree of substitution (DS) ranging from 1 to 10 %. Methyl methacrylate (MMA) was polymerized in DMSO/H2O to form graft chains with MW of 30-40 kDa and PDIs as low as 1.07. Self-assembled structures from this material were confirmed by TEM and DLS with sizes ranging from 80 to 150 nm. We are currently working on two different synthetic approaches to make alginate based amphiphilic polymers. First one is a ‘graft from’ strategy, where the hydrophilic polymer is polymerized directly from alginate. Second is a ‘graft to’ approach, where a polymer is synthesized first and then clicked onto alginate. Drug loading strategies based on polymer drug interaction by using two hydrophilic anti-cancer drugs are currently being developed.

Seminar Series

Radical Copolymerization of Hydroxy-functional Monomers: Kinetic and Semibatch Studies

Jan Schier ABSTRACT

Solvent-borne acrylic resins used as polymeric binders in automotive coatings or matrices for contact lenses are complex copolymers containing reactive functional (often hydroxyl) groups. A better understanding of the copolymerization kinetics of these monomers is required in order to ensure uniform distribution of the functional groups among the polymer chains over the course of production. Radical copolymerization propagation kinetics of 2-hydroxyethyl acrylate (HEA) with other acrylates and methacrylates are investigated both in bulk and solution, using high frequency (up too 500 Hz) pulsed-laser polymerization (PLP) combined with size exclusion chromatography (SEC) and proton NMR, with typical SEC output. The experiments show that copolymer composition and averaged propagation rate coefficients are affected by solvent choice relative to bulk polymerization due to hydrogen bonding interactions. In addition, it was found that H-bonding, caused by solvent choice or monomer functionalities significantly affects the backbiting mechanism of acrylates. These kinetic effects influence polymer molecular mass distributions and structure of hydroxy-functional acrylate copolymers formed by higher

temperature starved-feed semibatch reactions under industrially-relevant conditions.

Seminar Series

A Comparison of Deterministic and Stochastic Approaches for Modeling of Polymerization Kinetics

M. Ali Parsa ABSTRACT The Gillespie Monte Carlo algorithm for simulation of polymerization kinetics has been implemented to model polymer architectures difficult to represent by deterministic techniques. A comparison of the two methods is made in a simulation study of the distribution of functional groups in polymer chains produced in radical copolymerization by starved-feed semibatch operation. A deterministic model is formulated to separately track the homopolymer chains that are produced without the desired functionality, a Monte-Carlo (MC) model is written to represent the system, and a hybrid deterministic/MC approach is taken using new capabilities within the software package PREDICI®. Even under perfect control of overall copolymer composition, simulations indicate that almost half of the polymer chains produced (number-average length of 20, with a single functional group per chain on average) contains no functionality. As an additional example of the advantages of the Monte-Carlo method, the simulation of hyper-branched chain topology produced by ethylene polymerization with a Pd-diimine “chain-walking” catalyst is introduced.

Seminar Series

Effect of Anion Metathesis on the Mechanical Properties of Imidazolium Ionomer Derivatives of Isobutylene-rich Rubber

Antonio Cillero Rodrigo ABSTRACT Two imidazolium ionomer derivatives of poly(isobutylene-co-p-methylstyrene) (BIMS), the N-vinyl benzyl imidazolium bromide salt (IMS-VImBr) and the N-butyl benzyl imidazolium bromide salt of BIMS (IMS-BuImBr), were prepared by the N-alkylation of 1-vinylimidazole and 1-butylimidazole , respectively. A subsequent anion metathesis was performed in order to exchange bromide for other counter anions. The effect of anion metathesis on the mechanical and adhesive properties of these two ionomers was studied. The results demonstrated that the nature of the counter anion significantly affects the final properties of the ionomer suggesting that the counter anion plays a significant role in the structure of the ionic network formed by the aggregation of ionic groups.

Seminar Series

Delayed-Onset Peroxide Crosslinking Formulations Brian Molloy

ABSTRACT An acrylate functionalized nitroxyl radical, 4-acroyloxy-2,2,6,6-tetrmethylpiperidine-N-oxyl (AOTEMPO) is examined for its effect on the onset and yield of peroxide initiated crosslinking formulations in a variety of polymer systems. The ability of AOTEMPO to generate a cure in polymer systems that normally undergo degradation through chain scission in the presence of peroxides is also examined.