John Pojman

John Pojman
Louisiana State University | LSU · Department of Chemistry

Ph.D.

About

301
Publications
45,313
Reads
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8,842
Citations
Citations since 2017
35 Research Items
2983 Citations
20172018201920202021202220230100200300400500600
20172018201920202021202220230100200300400500600
20172018201920202021202220230100200300400500600
20172018201920202021202220230100200300400500600
Additional affiliations
January 2009 - present
Louisiana State University
January 1999 - present
Brandeis University
January 1996 - December 2012
University of Southern Mississippi

Publications

Publications (301)
Article
Full-text available
Culturing cancer cells in a three-dimensional (3D) environment better recapitulates in vivo conditions by mimicking cell-to-cell interactions and mass transfer limitations of metabolites, oxygen, and drugs. Recent drug studies have suggested that a high rate of preclinical and clinical failures results from mass transfer limitations associated with...
Article
Full-text available
Thermal frontal polymerization (FP) is a chemical process during which a cold monomer-initiator mixture is converted into a hot polymer as a polymerization front propagates in the system due to the interplay between heat diffusion and the exothermicity of the reaction. The theoretical description of FP generally focuses on one-dimensional (1D) reac...
Article
Frontal polymerization is a process in which a localized reaction zone propagates from the coupling of thermal transport and the Arrhenius rate dependence of an exothermic polymerization; monomer is converted into polymer as the front passes through an unstirred medium. Herein we report the first study of charge transfer complexes (CTCs) as photo/t...
Article
Full-text available
This work investigates experimentally and numerically frontal polymerization in a thermally anisotropic system with parallel copper strips embedded in 1,6-hexanediol diacrylate resin. Both experiments and multiphysics finite element analyses reveal that the front propagation in the thermally anisotropic system is orientation-dependent, leading to v...
Chapter
Frontal polymerization is a process in which a localized reaction zone propagates through monomer or monomers, leaving polymer in its wake, by the coupling of thermal transport and the Arrhenius dependence of the reaction rate of an exothermic polymerization. One-pot formulations with long shelf lives can be created that will cure rapidly when a fr...
Article
Full-text available
Frontal polymerization, which involves a self-propagating polymerizing reaction front, has been considered as a rapid, energy-efficient, and environmentally friendly methodology to manufacture lightweight, high-performance thermoset polymers, and composites. Previous work has reported that the introduction of thermally conductive elements can enhan...
Article
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The reaction and diffusion of small molecules is used to initiate the formation of protective polymeric layers, or biofilms, that attach cells to surfaces. Here, inspired by biofilm formation, we present a general method for the growth of hydrogels from urease enzyme-particles by combining production of ammonia with a pH-regulated polymerization re...
Article
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Microfluidic gradient generators have been used to study cellular migration, growth, and drug response in numerous biological systems. One type of device combines a hydrogel and polydimethylsiloxane (PDMS) to generate “flow-free” gradients; however, their requirements for either negative flow or external clamps to maintain fluid-tight seals between...
Article
Formulations containing vinyl ethers and epoxy were successfully polymerized through a radical‐induced cationic frontal polymerization mechanism, using an iodonium salt superacid generator with a peroxide thermal radical initiator and fumed silica as a filler. It was found that an increase of vinyl ether content resulted in higher front velocities...
Article
Full-text available
Using frontal polymerization to create controlled, programmable, and useful patterns in properties of a thermoset polymer without masks, molds, or printers.
Article
Novel bio‐based microparticles and latexes are synthesized using green chemistry principles through the reaction of aconitic acid (a sugarcane byproduct) and epoxidized linseed oil (ELO). No volatile solvents have been used, and no initiators are present in this polymerization. Using different agitation techniques, we investigate the particles and...
Article
Frontal polymerization (FP) is a process in which a front propagates in a localized reaction zone, converting monomer into polymer through the coupling of thermal diffusion with the Arrhenius kinetics of an exothermic reaction. Fillers are added to control the rheological properties of the formulation and to enhance the mechanical properties of the...
Article
Full-text available
There is significant interest in developing new approaches for culturing mammalian cells in a three‐dimensional (3D) environment due to the fact that it better recapitulates the in vivo environment. The goal of this work was to develop thiol‐acrylate, biodegradable hydrogels that possess highly tunable properties to support in vitro 3D culture. Six...
Article
Lignin readily dissolves in a deep eutectic solvent (DES) composed of ZnCl2/acetamide 1:3 molar ratio in concentrations up to 16.7 wt%, and upon addition of water, two fractions were obtained; one composed of lignin with low molecular weight that remained dissolved in the DES/water mixture while the other fraction of lignin with higher molecular we...
Article
Poly(dimethylsiloxane) (PDMS) is one of the dominant polymeric hydrophobic materials that has been widely used in microfluidic devices. Here, we employed amine-catalyzed thiol-acrylate chemistry with hydrophilic and fluorinated acrylates to produce a wide range of stable hydrophilic materials without use of expensive instrumentation or complicated...
Article
The kinetics of photopolymerization of and in deep eutectic solvents (DESs) has been investigated through real-time FTIR. The systems of this study were choline chloride DESs made of acrylic acid and methacrylic acid (DES monomers) and a non-reactive analog- isobutyric acid. The DES consisting of the analog also contained the monomer-methyl methacr...
Article
Frontal polymerization has been explored as a technique to form two-dimensional thin films (<0.5 mm) on wood. We used trimethylolpropane triacrylate with a thermal free-radical initiator. The viscosity of the resin was adjusted by incorporating fumed silica within the formulation. As filler materials, either calcium carbonate or graphene nanoplatel...
Article
Frontal polymerization is a method of converting monomer(s) to polymer via a localized reaction zone that propagates from the coupling of thermal diffusion with the Arrhenius kinetics of an exothermic reaction. Several factors affect front velocity and temperature with the role of monomer functionality being of particular interest in this study. Po...
Article
Full-text available
In theory, groups of enzyme-loaded particles producing an acid or base may show complex behavior including dynamical quorum sensing, the appearance of synchronized oscillations above a critical number or density of particles. Here, experiments were performed with the enzyme urease loaded into mm-sized agarose beads and placed in a solution of urea,...
Article
Full-text available
The bell-shaped reactivity-pH curve is the fundamental reason that the temporal programmable kinetic switch in clock reactions can be obtained in bio-competitive enzymatic reactions. In this work, urease was loaded on small resin particles through ionic binding. Experimental results reveal that the immobilization not only increased the stability of...
Article
Full-text available
Thiol-acrylate polymers have therapeutic potential as biocompatible scaffolds for bone tissue regeneration. Synthesis of a novel cyto-compatible and biodegradable polymer composed of trimethylolpropane ethoxylate triacrylate-trimethylolpropane tris (3-mercaptopropionate) (TMPeTA-TMPTMP) using a simple amine-catalyzed Michael addition reaction is re...
Article
Frontal polymerization is way to convert liquid resin into a solid material with a self-propagating reaction. The reaction spreads like a flame from the heat of the reaction that diffuses into neighboring regions, starting more reaction. The frontal velocity has been accurately modeled for free-radical polymerization systems. The dynamics of fronts...
Article
Full-text available
Correction for ‘Porous monoliths synthesized via polymerization of styrene and divinyl benzene in nonaqueous deep-eutectic solvent-based HIPEs’ by M. G. Pérez-García et al. , RSC Adv. , 2015, 5 , 23255–23260.
Article
Full-text available
Fingering is a hydrodynamic instability that occurs when a more mobile fluid displaces a fluid of lower mobility. When the primary source of the mobility difference is viscosity, the instability is termed viscous fingering. Viscous fingering is often, though not always, undesirable in industrial processes, particularly secondary petroleum recovery....
Article
Full-text available
Amphibian skin is unique among vertebrate classes, containing a large number of multicellular exocrine glands that vary among species and have diverse functions. The secretions of skin glands contain a rich array of bioactive compounds including antimicrobial peptides (AMPs). Such compounds are important for amphibian innate immune responses and ma...
Article
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The increasing environmental awareness has led to the search of alternative reaction media to reduce or eliminate the use of organic solvents in polymer science. Deep eutectic solvents (DESs), a subclass of ionic liquids, have emerged as sustainable solvents for a plethora of chemical reactions. In this Trend Article, DES utilization in free-radica...
Article
The effect of pseudo-gravitational acceleration on the dissolution process of two phase miscible systems has been investigated at high acceleration values using a spinning drop tensiometer with three systems: 1-butanol/water, isobutyric acid/water, and triethylamine/water. We concluded that the dissolution process involves at least three different...
Article
Full-text available
Viscous fingering can occur in fluid motion whenever a high mobility fluid displaces a low mobility fluid in a Darcy type flow. When the mobility difference is primarily attributable to viscosity (e.g., flow between the two horizontal plates of a Hele–Shaw cell), viscous fingering (VF) occurs, which is sometimes termed the Saffman–Taylor instabilit...
Article
Full-text available
An acrylamide-based chemical grouting system has been developed that allows users to initiate the curing process on demand. After heating a localized area, the curing reaction propagates through the grout via a process called frontal polymerization. The system was engineered so that the grout would eventually cure without user input, as with curren...
Article
Full-text available
A new deep eutectic solvent (DES) was developed as a phase selective gelator for oil-spill remediation. The newly designed non-ionic DES is based on a combination of an amide (N-methylacetamide) and a long chain carboxylic acid (lauric acid) and does not require any synthetic procedure besides mixing. Our studies show that the DES works as gelator...
Article
Frontal polymerization of deep eutectic solvents (DESs) made with acrylic or methacrylic acid as the monomer and hydrogen bond donor was studied. Fronts with acrylic acid and choline chloride propagated more uniformly than with pure acrylic acid, so an exploration into how the DES affected frontal polymerization was performed. The hydrogen bond acc...
Article
Nonaqueous high internal phase emulsions (HIPEs) stabilized by nanohydroxyapatite (NHA)/surfactant hybrids are used as template to prepare interconnected porous monoliths. The use of a sustainable deep eutectic solvent (DES) comprised of urea and choline chloride (UChCl), as the internal phase, enables an efficient interaction of NHA/surfactant at...
Article
We report an alternative green strategy based on deep-eutectic solvents (DES) to deliver multi-walled carbon nanotubes (MWCNTs) for a bottom-up approach that allowing the selective interfacial functionalization of nonaqueous poly(high internal phase emulsions), poly(HIPEs). The formation and polymerization of methacrylic and styrenic HIPEs were pos...
Article
High internal phase emulsions are an interesting emulsion subset attainable by surpassing the critical volume of uniform spherical arrangement resulting in a new metastable polyhedral motif. By profiting from their stability time frame and through the introduction of a polymerizable phase, these unique structures can be “locked” in place, affording...
Article
Full-text available
We studied the effect of anionic, cationic, and nonionic surfactants on the interfacial tension between the two phases of the isobutyric acid/water system using spinning drop tensiometry. It has been found that interfacial tension decreases with increasing concentration of the surfactant in the case of sodium dodecyl sulfate (SDS) and of dodecyltri...
Article
Full-text available
Dermatophagy, the practice of eating shed skin, in amphibians and reptiles has been reported anecdotally in the literature, but the process and purpose remains poorly understood. We document a fortuitous observation of whole-skin shedding and conspecific dermatophagy in Amphiuma tridactylum (Three-toed Amphiuma), and report on 2 additional observat...
Article
We demonstrated for the first time a cure-on-demand wood adhesive using thermal frontal polymerization with Southern Pine wood. Monomer structure, initiator loading, and filler loading all had an impact on the strength of the adhesive and the cure-on-demand ability. More flexible, ethoxylated monomers produced stronger adhesives; though, the ethoxy...
Article
We report a simple route to produce chitin films with different crystalline structures. The use of the green deep-eutectic solvent (DES) choline chloride:urea (CCU) or hexafluoroisopropanol (HFIP) allows fine-tunning of the crystallization process to produce β-dihydrated- and γ-chitn structures. With the advent of Grazing-Incidence X-Ray Diffractio...
Article
A piston driven shallow bed reactor (5.9 cm high) was used to conduct suspension polymerization under unstable flow conditions, which produced excellent mixing and droplet breakage. The instability started at the air-solution interface and carried through to the complete solution volume. The liquid interfacial instability described in the classic p...
Article
Full-text available
Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease-catalyzed hydrolysis of urea was used to trigger the base-catalyzed Michael addition of a...
Article
Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease-catalyzed hydrolysis of urea was used to trigger the base-catalyzed Michael addition of a...
Article
Choline chloride-ZnCl2 deep-eutectic solvent (ChCl-ZnCl2 DES), mole ratio 1 : 2, was used to improve the chemical reactivity of wheat straw alkali lignin under different temperatures and times of pretreatment. The chemical structure of resulting modified lignin was studied by UV, FT-IR, 1H, 13C and 31P-NMR spectroscopies, TGA, NALDI-TOF MS and ICP....
Conference Paper
The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyze...
Article
Full-text available
We demonstrate thiol-acrylate microfluidics prepared via soft lithography for single-step protein immobilization and fluorescence-based pathogen detection. Such microfluidics are formed via room temperature curing, and bonded without oxygen plasma. The background fluorescence of the resin was found to be similar to PDMS for several filter sets. We...
Article
Because of the large number of total knee replacement (TKR) surgeries conducted per year, and with projections of increased demand to almost a million primary TKR surgeries per year by 2030 in the United States alone, there is a need to discover more efficient working materials as alternatives to current bone cements. There is a need for surgeons a...
Article
Microencapsulation of a material is often used when a controlled release of a substance is desired. This study examines the effects of crosslinking in polyurea microcapsule shells on stability of microcapsules containing the free-radical initiator cumene hydroperoxide (CHP). Crosslinking of polyurea shells was varied by using amine monomers contain...
Article
Full-text available
The main goal of our research deals with a new greener and more efficient lignin modification method to optimize its structural performance as phenol-formaldehyde resin filler. Through the appropriate increase in the phenolic hydroxyl content, an added value as a raw material was intended. For that, a series of mixtures of zinc chloride/urea with d...
Article
Full-text available
Stable nonaqueous high internal phase emulsions (HIPEs) were prepared and thermally polymerized to yield poly(HIPEs). The internal phase accounting for 80 vol.% of the HIPE consisted of a deep-eutectic solvent (DES) while the continuous one comprised styrene and divinyl benzene in a 10:1 molar ratio. DESs with different viscosities were used as an...
Article
Functionally gradient materials (FGMs) with gradual and continuous changes of their properties in one or more dimensions are useful in a wide range of applications. However, obtaining such materials with accurate control of the gradient, especially when the gradient is non-linear, is not easy. In this work, frontal polymerization (FP) was exploited...
Article
Full-text available
We study the spatio-temporal evolution of the viscosity field during stable and unstable radial flows of glycerol-water solutions in a horizontal Hele-Shaw cell where a localized temperature gradient is imposed. The viscosity field is reconstructed from themeasurement of the fluorescence emitted by a viscosity-sensitive molecular probe (Auramine O)...
Article
As of 2010, 5.3 million orthopedic surgeries are performed each year, and this number is expected to increase to 6.2 million by 2020. On average, 27.7% of all orthopedic surgeries result in infection which often leads to osteomyelitis and the loss of supporting bone. In this study, we describe two synthetic bone grafts, or augmentation methods, for...
Article
Full-text available
This work takes advantage of the transformation of lidocaine hydrochloride into deep-eutectic solvents (DESs) -ionic liquid analogues- to incorporate polymerizable counterparts into DES, such that polymer-drug complexes are synthesized by free-radical frontal polymerization without the use of solvent. DESs are formed through hydrogen bonding of an...
Article
Full-text available
This study demonstrates the formation and polymerization of high internal phase emulsions (HIPEs) with (meth)acrylic monomers as continuous phase and urea-choline chloride deep-eutectic solvent as a favorable nonaqueous internal phase. After recovering of DES, resultant poly(HIPEs) showed interconnected macroporosity which can be tuned by varying t...
Article
Full-text available
A thiol-acrylate based copolymer synthesized via an amine-catalyzed Michael addition was studied in vitro and in vivo to assess its potential as an in situ polymerizing graft or augment in bone defect repair. The blends of hydroxyapatite (HA) with pentaerythritol triacrylate-co-trimethylolpropane (PETA), cast as solids or gas foamed as porous scaff...
Article
Thermal frontal polymerization was carried out with trimethylol propane triglycidyl ether using two different BF3-amine complexes, B-950 and B-110 from Leepoxy, as initiators for cationic polymerization. The amounts of filler (kaolin or fumed silica), defoaming, or expansion agents were varied to study how the compositions affected the front veloci...
Article
Full-text available
In this study, we present an inexpensive and practical method that allows the monitoring and visualization of front polymerization, propagation, and dynamics. Commercially available europium-doped aluminum oxide powders were combined with video imaging to visualize free-radical propagating polymer fronts. In order to demonstrate the applicability o...
Article
Dynamic rheology in combination with Fourier transform infrared spectroscopy (FTIR) is used to examine the gelation kinetics, mechanism, and gel point of novel thiol−acrylate systems containing varying concentrations of an in situ catalyst. Gelation, as evidenced from the gel time determined using the Winter− Chambon criterion, is found to occur mo...
Article
Bone tissue engineering approaches using polymer/ceramic composites show promise as effective biocompatible, absorbable, and osteoinductive materials. A novel class of in situ polymerizing thiol-acrylate based copolymers synthesized via an amine-catalyzed Michael addition was studied for its potential to be used in bone defect repair. Both pentaery...
Data
In an effort to create frontal polymerization systems with a "fail-safe" curing mechanism, we studied the effects of thiols on the thermal frontal polymerization velocity and pot life of a mixture of a multifunctional acrylate, kaolin clay (filler), and cumene hydroperoxide with either trimethylolpropane tris(3-mercaptopropionate) or 1-dodecanethio...
Article
The deep eutectic solvents (DESs) based on the mixtures of a variety of ammonium salts and hydrogen bond donors containing acrylic acids and acrylamides are capable of sustaining frontal polymerization (FP). The selection of ammonium salt affects the reactivity and allows FP at relatively low temperature but with full conversion. Also, full convers...
Article
In situ tertiary amine-catalyzed thiol-acrylate chemistry was employed to produce hydrophilic microfluidic devices via a soft lithography process. The process involved the Michael addition of a secondary amine to a multifunctional acrylate producing a nonvolatile in situ tertiary amine catalyst/comonomer molecule. The Michael addition of a multifun...
Article
Full-text available
Frontal polymerization (FP) is a process in which a localized reaction zone propagates through monomer or monomers, leaving polymer in its wake. There are three types of FP. The first is photofrontal polymerization in which the front is driven by the continuous flux of radiation, usually UV light. The second is isothermal frontal polymerization, wh...
Article
The urease-catalyzed hydrolysis of urea displays feedback that results in a switch from acid (pH ~3) to base (pH ~9) after a controllable period of time (from 10 to >5000 s). Here we show that the spatially distributed reaction can support pH wave fronts propagating with a speed of the order of 0.1�1 mm min �1. The experimental results were reprodu...
Article
We studied thermal frontal polymerization using a redox system in an attempt to lower the temperature of the frontally polymerizable system while increasing the front velocity so as to obtain a self-sustaining front in a thinner layer than without the redox components. A cobalt-containing polymer with a melting point of 63 °C (Intelimer 6050X11) an...
Article
Reaction-driven pattern formation at the interface between two thin liquid films is studied experimentally on a vertical substrate when two organic liquids, an acrylate and a secondary amine, respectively, are put in contact. On a clean glass plate, the pure liquids spread without any instability and no film deformation is observed. On the contrary...
Article
We report a novel approach to prepare microparticles via a dispersion polymerization using the amine-catalyzed addition of a trithiol to a triacrylate. Microparticles loaded with various core materials were produced and applied in various systems to improve the desired characteristics of the given system. We determined that this type of micropartic...
Article
Full-text available
Sodium polyacrylate-induced pH pattern formation and starch-induced iodine pattern formation were investigated in the iodate-sulfite-thiosulfate (IST) reaction in a one-side fed disc gel reactor (OSFR). As binding agents of the autocatalyst of hydrogen ions or iodide ions, different content of sodium polyacrylate or starch has induced various types...