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Publications (21)
Ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) with diameters < 5 nm hold great promise as T1-positive contrast agents for in vivo magnetic resonance imaging (MRI). However, control of the surface chemistry of USPIOs to ensure individual colloidal USPIOs with a ligand monolayer and to impart biocompatibility and enhanced colloidal s...
Copper(0)-mediated controlled radical polymerization (CRP), or single-electron transfer-living radical polymerization (SET-LRP) is a robust and dynamic technique that has attracted considerable academic and industrial interest as a synthetic tool for novel value-added materials. Although SET-LRP possesses many advantages over other forms of CRP, th...
A new strategy that centers on the incorporation of stimuli-responsive cleavable linkages in dual or multiple locations as in both micellar cores and at polymer/solution interfaces leading to synergistically enhanced release of encapsulated anticancer drugs in cancer cells.
The use of copper tubing as both the reactor and as a catalyst source is demonstrated for continuous controlled radical polymerization of methyl acrylate at ambient temperature and at low solvent content of 30%. The high surface area provided by the copper walls mediates the reaction via the single electron transfer-living radical polymerization (S...
Controlled radical polymerization of methyl acrylate catalyzed by copper was conducted in a continuous tubular reactor. A length of copper tubing was used to initiate polymerization and generate soluble copper species, while the bulk of polymerization took place in inert stainless steel tubing. To mediate polymerization in the absence of copper sur...
Colloidal superparamagnetic iron oxide nanoparticles (SNPs) have been a preferred choice for biocompatible contrast agents in magnetic resonance imaging (MRI) in vivo. One remaining critical challenge is the control over surface chemistry of colloidal SNPs to retain biocompatibility and colloidal stability under harsh physiological conditions. This...
Stimuli-responsive degradation (SRD) based on disulfide chemistry is highly desirable in the development of self-assembled block copolymer nanocarriers for multifunctional polymer-based drug delivery systems. In contrast to most conventional approaches involving the incorporation of disulfide linkages at single locations, an effective dual location...
A multidentate block copolymer (MDBC) strategy to stabilize ultrasmall superparamagnetic iron oxide nanoparticles (USNPs) as biocompatible T1-positive contrast agents for magnetic resonance imaging (MRI) is explored. The MDBC is designed with a poly(methacrylic acid) (PMAA) block having pendant carboxylates as multidentate anchoring groups and a hy...
New poly(ethylene oxide)-based block copolymers (ssBCs) with a random copolymer block consisting of a reduction-responsive disulfide-labeled methacrylate (HMssEt) and a thermoresponsive di(ethylene glycol)-containing methacrylate (MEO2MA) units were synthesized. The ratio of HMssEt/MEO2MA units in the random P(MEO2MA-co-HMssEt) copolymer block enab...
Well-defined amphiphilic block copolymers (ABPs) consisting of poly(oligo(ethylene oxide) monomethyl ether methacrylate) (POEOMA) and poly(tert-butyl methacrylate) (PtBMA) were successfully synthesized using an activator regenerated by electron transfer (ARGET) process for atom transfer radical polymerization (ATRP). Two synthetic routes starting f...
The synthesis, tunable thermoresponsive properties, and self-assembly of dual redox and thermoresponsive double hydrophilic block copolymers having pendant disulfide linkages (DHBCss) are reported. Well-defined DHBCss composed of a hydrophilic poly(ethylene oxide) block and a dual thermo- and reduction-responsive random copolymer block containing p...
Amphiphilic block copolymer-based micellar nanocarriers hold great promise as a drug delivery platform; however, the colloidal stability of nanoassemblies upon intravenous injection remains a significant challenge. Further, enhanced/controlled release of encapsulated drugs by cleavage of dynamic covalent linkages in response to external stimuli is...
A facile strategy to fabricate thiol-responsive thermoresponsive hydrogels able to rapidly change their volume in response to temperature is reported. The strategy utilizes crosslinking atom transfer radical polymerization to synthesize well-defined hydrogels of thermoresponsive oligo(ethylene oxide)-based polymethacrylates with a uniform network c...
Activator regenerated by electron transfer atom-transfer radical polymerization of butyl acrylate and methyl methacrylate was successfully adapted from a batch process to a continuous stirred tank reactor (CSTR) with 50 ppm copper. A series of batch polymerizations were first performed to identify a solvent mixture to enhance the polymerization rat...
A new approach that centers on modulating the hydrophobic-hydrophilic balance by conversion of pendant disulfides to thiols and further to sulfides enables facile tuning of the thermoresponsive properties of thiol-responsive copolymers.
The controlled radical polymerization of methyl acrylate in DMSO mediated by copper wire in a continuous stirred tank reactor (CSTR) was successfully demonstrated. Copper wire proved to be an easy to handle and reusable catalyst source, mediating chain growth through the SET-LRP mechanism. Polymerizations were conducted at 30 °C for three different...
An overview of solution ATRPs carried out in batch, semibatch and continuous tubular and stirred‐tank reactor systems is presented. Initial work using a heterogeneous catalyst system with copper to polymer chain ratios of close to unity demonstrated the versatility of ATRP in producing homopolymer and copolymer at reasonable rates with good MW cont...
Continuous ARGET ATRP of butyl methacrylate was carried out in an 850 mL tubular reactor using parts per million levels of copper catalyst and stoichiometric amounts of ligand to copper under industrially relevant conditions without monomer and solvent purification. A copper(II) bromide/tris(2‐pyridylmethyl)amine complex was used as catalyst, and t...
Atom transfer radical polymerizations of butyl methacrylate, methyl methacrylate, and butyl acrylate were conducted using only ppm amounts of catalyst through the regeneration of activator via the ARGET mechanism. The polymers produced were nearly colorless, and exhibited living characteristics with copper catalyst levels as low as 6.4 ppm (relativ...
