Facile synthesis of poly(hydroxyethyl acrylate) by frontal free‐radical polymerization

We report the first synthesis of poly(hydroxyethyl acrylate) (PHEA) without solvent by free‐radical frontal polymerization (FP) at ambient pressure. In a typical run, the appropriate amounts of reactant (hydroxyethyl acrylate) and initiator (1,1‐di(tert‐butylperoxy)‐3,3,5‐trimethylcyclohexane) (Luperox 231) were mixed together at ambient pressure. FP was initiated by heating the wall of the tube with a soldering iron, and the resultant hot fronts were allowed to self‐propagate throughout the reaction vessel. Once initiated, no further energy was required for polymerization to occur. To study the macrokinetics, we also produced PHEA frontally with ammonium persulfate as initiator and dimethyl sulfoxide as the solvent. The dependences of the front velocity and front temperature on the initiator concentration and reactant dilution were investigated. The front temperatures were between 124 and 157 °C, depending on the ammonium persulfate concentration. Thermogravimetric analysis indicates that PHEA prepared by FP with ammonium persulfate as initiator had higher thermal stability than solvent‐free frontally prepared PHEA with Luperox 231 as initiator. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 873–881, 2007     

Block copolymer composition drives function of self‐assembled nanoparticles for delivery of small‐molecule cargo

Nanoparticles are useful for the delivery of small molecule therapeutics, increasing their solubility, in vivo residence time, and stability. Here, we used organocatalytic ring opening polymerization to produce amphiphilic block copolymers for the formation of nanoparticle drug carriers with enhanced stability, cargo encapsulation, and sustained delivery. These polymers comprised blocks of poly(ethylene glycol) (PEG), poly(valerolactone) (PVL), and poly(lactide) (PLA). Four particle chemistries were examined: (a) PEG‐PLA, (b) PEG‐PVL, (c) a physical mixture of PEG–PLA and PEG–PVL, and (d) PEG–PVL–PLA tri‐block copolymers. Nanoparticle stability was assessed at room temperature (20 °C; pH = 7), physiological temperature (37 °C; pH = 7), in acidic media (37 °C; pH = 2), and with a digestive enzyme (lipase; 37 °C; pH = 7.4). PVL‐based nanoparticles demonstrated the highest level of stability at room temperature, 37 °C and acidic conditions, but were rapidly degraded by lipase. Moreover, PVL‐based nanoparticles demonstrated good cargo encapsulation, but rapid release. In contrast, PLA‐based nanoparticles demonstrated poor stability and encapsulation, but sustained release. The PEG–PVL–PLA nanoparticles exhibited the best combination of stability, encapsulation, and release properties. Our results demonstrate the ability to tune nanoparticle properties by modifying the polymeric architecture and composition. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1322–1332     

A facile pathway for the fast synthesis of colloidal crystal‐loaded hydrogels via frontal polymerization

In this work, a dually sensitive colloidal crystal (CC)‐loaded hydrogel has been synthesized via frontal polymerization (FP) in a facile and rapid way. First, a polystyrene CC film was fabricated by vertical deposition on the inner wall of a test tube. Then, a mixture of acrylic acid (AAc), 2‐hydroxyethyl methacrylate (HEMA), and glycerol along with the initiator and crosslinker was added to this test tube to carry out FP, resulting in the formation of CC‐loaded hydrogel. The influence of the mass ratios of HEMA/AAc on front velocity and temperatures were studied. The swelling behavior, the morphology, and the stimuli‐responsive behavior of the CC‐loaded hydrogels prepared via FP were thoroughly investigated on the basis of swelling measurement, scanning electron microscopy, and reflection spectra. Results show that the as‐prepared CC‐loaded hydrogels exhibit excellent dual sensitivity to both methanol concentrations and pH values with very short response time, which can be observed visually without the aid of instruments. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Facile synthesis of amphiphilic gels by frontal free‐radical polymerization

We report a new facile strategy for quickly synthesizing poly(2‐hydroxyethyl acrylate‐co‐vinyl versatate) amphiphilic gels with excellent physicochemical properties by frontal free‐radical polymerization. The appropriate amounts of 2‐hydroxyethyl acrylate, vinyl versatate (VeoVa 9) and ammonium persulfate initiator were mixed together at ambient temperature in the presence of N‐methyl‐2‐pyrrolidone as the solvent medium. Frontal polymerization (FP) was initiated by heating the wall of the tube with a soldering iron. Once initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the initiator concentration was investigated. The front temperatures were between 132 and 157 °C, depending on the initiator concentration. The morphology, swelling rate, and swelling behavior of amphiphilic gels prepared via FP were comparatively investigated on the basis of scanning electron microscopy, water contact angle, and swelling measurements. Results show that the amphiphilic gels prepared via FP behave with good swelling capacity both in water and organic solvents. The FP can be exploited as an alternative means for synthesis of amphiphilic gels with additional advantages of fast and efficient way. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 823–831, 2010     

pH‐ and temperature‐sensitive statistical copolymers poly[2‐(dimethylamino)ethyl methacrylate‐stat‐2‐vinylpyridine] with Functional succinimidyl‐ester chain ends synthesized by nitroxide‐mediated polymerization

Statistical copolymerizations of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) with 2‐vinylpyridine (2VP) with 80 to 99 mol % DMAEMA in the feed utilizing a succinimidyl ester‐terminated alkoxyamine unimolecular initiator (NHS‐BlocBuilder) at 80 °C in bulk were performed. The effectiveness of 2VP as a controlling comonomer is demonstrated by linear increases in number‐average molecular weight versus conversion, relatively low PDI (1.5–1.6 with up to 98% DMAEMA) and successful chain extensions with 2VP. Additional free nitroxide does not significantly improve control for the DMAEMA/2VP copolymerizations. The succinimidyl ester on the initiator permits coupling to amine‐terminated poly(propylene glycol) (PPG), yielding an effective macroinitiator for synthesizing a doubly thermo‐responsive block copolymer of PPG‐block‐P(DMAEMA/2VP). A detailed study of the thermo‐ and pH‐sensitivities of the statistical and block copolymers is also presented. The cloud point temperature of the statistical copolymers is fine tuned from 14 to 75 °C by varying polymer composition and pH. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.     

Frontal cationic curing of epoxy resins

We studied the frontal curing of trimethylolpropane triglycidyl ether (TMPTGE) using two BF₃‐amine initiators and two fillers, kaolin and fumed silica. In the case of kaolin, the range of concentrations allowing for frontal polymerization to propagate was dependent on its heat absorption effect whereas in the case of silica it was a consequence of the rheological features of this additive. However, for both systems the velocity and front temperature show the same trends; in all cases front velocities were on the order of 1 cm/min with front temperatures about 200 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2000–2005, 2010     

Thermal frontal polymerization with a thermally released redox catalyst

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) and cumene hydroperoxide were used with a triacrylate. The use of the Intelimer decreased the front velocity but allowed fronts to propagate in thinner layers and with more filler while still having a pot life of days. Nonplanar modes of propagation occurred. Fronts propagated faster when 6‐O‐palmitoyl‐L ‐ascorbic acid was used as a reductant. Interestingly, fronts were also faster with the reductant even without the Intelimer if kaolin clay was the filler; however, the pot life was significantly reduced. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Double responsive copolymer hydrogels prepared by frontal polymerization

Frontal polymerization was successfully used to synthesize copolymer hydrogels of poly(N‐vinylcaprolactam‐co‐itaconic acid). All materials were characterized by response to stimuli (pH and/or temperature), depending on the itaconic acid content. Namely, relatively low amounts of this latter were found to be crucial for determining the degree of swelling. In particular, hydrogels behave differently if swollen at pH values that are higher or lower of 7–8, and exhibit temperature response as well (lower critical solution temperature at ca. 30 °C), which makes these materials potentially interesting for biomedical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2166–2170     

Synthesis and characterization of original alternated fluorinated copolymers bearing glycidyl carbonate side groups

A vinyl ether bearing a carbonate side group (2‐oxo‐1,3‐dioxolan‐4‐yl‐methyl vinyl ether, GCVE) was synthesized and copolymerized with various commercially available fluoroolefins [chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and perfluoromethyl vinyl ether (PMVE)] by radical copolymerization initiated by tert‐butyl peroxypivalate. Although HFP, PMVE, and vinyl ether do not homopolymerize under radical conditions, they copolymerized easily yielding alternating poly(GCVE‐alt‐F‐alkene) copolymers. These alternating structures were confirmed by elemental analysis as well as ¹H, ¹⁹F, and ¹³C NMR spectroscopy. All copolymers were obtained in good yield (73–85%), with molecular weights ranging from 3900 to 4600 g mol^?1 and polydispersities below 2.0. Their thermogravimetric analyses under air showed decomposition temperatures at 10% weight loss (T_d,10%) in the 284–330°C range. The HFP‐based copolymer exhibited a better thermal stability than those based on CTFE and PMVE. The glass transition temperatures were in the 15–65°C range. These original copolymers may find potential interest as polymer electrolytes in lithium ions batteries. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Stimuli‐responsive 4‐acryloylmorpholine/4‐acryloylpiperidine copolymers via nitroxide mediated polymerization

4‐acryloylmorpholine/4‐acryloylpiperidine statistical copolymers were synthesized by nitroxide mediated polymerization (NMP) with BlocBuilder unimolecular initiator in dimethylformamide solution at 120 °C. The copolymers had narrow molecular weight distributions (dispersity ? = 1.25–1.35, number average molecular weights M _n = 8.5–13.7 kg mol^?1). The copolymer microstructure was essentially statistical (reactivity ratios r _4AP = 0.81 ± 0.73, r _4AM = 0.73 ± 0.68 based on non‐linear fitting of the Mayo‐Lewis equation). Cloud point temperatures (CPT) in aqueous media were tuned from 11 °C to 92 °C, merely by adjusting the initial monomer composition. Using NMP permitted sharper control of the CPT transitions, compared to the similar copolymer made using conventional radical polymerization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2160–2170     

Facile synthesis of N‐vinylimidazole‐based hydrogels via frontal polymerization and investigation of their performance on adsorption of copper ions

We report a new facile strategy for quickly synthesizing pH sensitive poly(VI‐co‐HEA) hydrogels (VI = N‐vinylimidazole; HEA = 2‐hydroxyethyl acrylate) by frontal polymerization. The appropriate amounts of VI, HEA, and ammonium persulfate (APS)/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) couple redox initiator were mixed together at ambient temperature in the presence of glycerol as the solvent medium. Frontal polymerization (FP) was initiated by heating the upper side of the mixture with a soldering iron. Once initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the VI/HEA weight ratios were investigated. The pH sensitive behavior, morphology, and heavy metal removal study of poly(VI‐co‐HEA) hydrogels prepared via FP were comparatively investigated on the basis of swelling measurements, scanning electron microscopy, and inductively coupling plasma spectrometer. Results show that the poly(VI‐co‐HEA) hydrogels prepared via FP exhibit good pH sensitivity and adsorption capacity. The FP can be exploited as an alternative means for synthesis of pH sensitive hydrogels in a fast and efficient way. The as‐prepared hydrogels can be applied to remove heavy metals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4005–4012, 2010     

Dual stimuli‐responsive polyamines derived from modified N‐vinylpyrrolidones through CuAAC click chemistry

The synthesis via copper(I)‐catalyzed azide alkyne cycloaddition (CuAAC) of three new monomer derivatives of N‐vinyl‐2‐pyrrolidone (VP) carrying cyclic pyrrolidine, piperidine, and piperazine groups and the corresponding copolymers with unmodified VP is shown. The systems bearing pyrrolidine and piperidine displayed both thermo‐ and pH‐response, which has not been reported previously for a polymer with polyvinylpyrrolidone (PVP) backbone. A broad modulation of the LCST with the copolymer composition and pH was observed in a temperature range 0–100 °C. The polymers carrying piperazine exhibited broad buffering regions and no thermosensitivity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1098–1108     

Carbohydrate‐based copolyesters made from bicyclic acetalized galactaric acid

Mixtures of the dimethyl esters of adipic acid and 2,3:4,5‐di‐O‐methylene‐galactaric acid (Galx) were made to react in the melt with either 1,6‐hexanediol or 1,12‐dodecanediol to produce linear polycyclic copolyesters with aldarate unit contents varying from 10 up to 90 mole %. The copolyesters had weight–average molecular weights in the ～35,000–45,000 g mol^?1 range and a random microstructure, and were thermally stable up to nearly 300 °C. They displayed T_g in the ‐50 to ‐7 °C range with values largely increasing with the content in galactarate units. All the copolyesters were semicrystalline with T_m between 20 and 90 °C but only those made from 1,12‐dodecanediol were able to crystallize from the melt at a crystallization rate that decreased as the contents in the two comonomers approached each other. Copolyesters containing minor amounts of galactarate units adopted the crystal structure characteristic of aliphatic polyesters but a new crystal polymorph was formed when the cyclic sugar units became the majority. Stress–strain parameters were sensitively affected by composition of the copolyesters with the mechanical behavior changing from flexible/ductile to stiff/brittle with the replacement of adipate units by the galactarate units. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Vinyl phenylboronic acid controlling co‐monomer for nitroxide mediated synthesis of thermoresponsive poly(2‐N morpholinoethyl methacrylate)

Low concentrations of 4‐vinylphenylboronic acid (VPBA) were copolymerized with 2‐N‐morpholinoethyl methacrylate (MEMA) by nitroxide mediated polymerization using BlocBuilder? unimolecular initiator at 80 to 90 °C. The MEMA/VPBA copolymerizations were performed at initial feed compositions (f_VPBA,0) of 0.05 to 0.10 VPBA, with f_VPBA,0 = 0.10 using dimethylacetamide (DMAc) solvent being most effective, as seen by a linear increase in number average molecular weight, M_n, versus conversion and low dispersity, ? < 1.40. The copolymers were further chain‐extended with a second batch of VPBA, resulting in a block copolymer with monomodal molecular weight distribution and ? = 1.66. For MEMA/VPBA copolymers, increases in VPBA composition and polymer solution concentration resulted in decreases in the cloud point temperature (CPT, typically varied between 27.4–37.8 °C) and CPT increased from 31.2 to 33.8 °C to about 88 °C with decreases in pH from 7 to 4. Rheological tests with small angle light scattering (SALS) confirmed CPTs measured by UV‐Vis and DLS. These copolymers were targeted as models to combine possible glucose‐sensing boronic acid functionality the thermoresponsiveness provided by MEMA groups. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1560–1572     

Frontal free‐radical copolymerization of urethane–acrylates

We report the first synthesis of urethane–acrylate copolymers via free‐radical frontal polymerization. In a typical run, the appropriate amounts of the reactants (urethane–acrylate macromonomer and 2‐hydroxyethyl acrylate) and initiator (ammonium persulfate) were dissolved in dimethyl sulfoxide. Frontal polymerization was initiated by the heating of the wall of the tube with a soldering iron, and the resultant hot fronts were allowed to self‐propagate throughout the reaction vessel. Once it was initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the initiator concentration was investigated. The front temperatures were between 55 and 65 °C, depending on the persulfate concentration. Thermogravimetric analysis indicated that the urethane–acrylate copolymers had higher thermal stability than pure frontally prepared polyurethane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3018–3024, 2006     

Photo‐triggered redox frontal polymerization: A new tool for synthesizing thermally sensitive materials

A novel approach of photo‐triggered redox frontal polymerization (FP) by integrating photocaged superbase (QA‐DBU) with a peroxide initiator (dibenzoyl peroxide, BPO) is presented for the synthesis of thermally sensitive materials. Under photo‐irradiation at a localized region, the regenerated superbase can diffuse into unirradiated regions and effectively actuate redox FP in a diffusion‐controlled manner. Moreover, the redox FP can be conducted at a much lower front temperature with enhanced front velocity. Astonishingly, the front temperature can be well‐modulated by changing the concentration of latent superbase. The prepared thermally sensitive fluorescent polymer composites exhibit enhanced fluorescence emission intensity compared to that of conventional thermal FP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4515–4521     

Stimulus‐responsive polymers based on 2‐hydroxypropyl acrylate prepared by RAFT polymerization

Homopolymerization and diblock copolymerization of 2‐hydroxypropyl acrylate (HPA) has been conducted using reversible addition fragmentation chain transfer (RAFT) chemistry in tert‐butanol at 80 °C. PHPA homopolymers were obtained with high conversions and narrow molecular weight distributions over a wide range of target degrees of polymerization. Like its poly(2‐hydroxyethyl methacrylate) isomer, PHPA homopolymer exhibits inverse temperature solubility in dilute aqueous solution, with cloud points increasing systematically on lowering the mean chain length. The nature of the end groups is shown to significantly affect the cloud point, whereas no effect of concentration was observed over the PHPA concentration range investigated. Various thermoresponsive PHPA‐based diblock copolymers were prepared via one‐pot syntheses in which the second block was either permanently hydrophilic or pH‐responsive. Preliminary studies confirmed that poly(ethylene oxide)‐poly(2‐hydroxypropyl acrylate) (PEO₄₅‐PHPA₄₈) and poly(2‐hydroxypropyl acrylate)‐ poly(2‐hydroxyethyl acrylate) (PHPA₄₉‐PHEA₆₈)diblock copolymers formed well‐defined PHPA‐core micelles in 10 mM sodium nitrate solution at 40 °C and 70 °C with mean hydrodynamic diameters of 20 nm and 35 nm, respectively. In contrast, most other PHPA‐based diblock copolymers investigated formed larger colloidal aggregates in 10 mM NaNO₃ solution at elevated temperatures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2032–2043, 2010     

Stable heterocumulene monomer in water; Synthesis and polymerization of (meth)acrylates having an isothiocyanate structure

Novel methacrylate and acrylate monomers having an isothiocyanate structure, 2‐isothiocyanatoethyl methacrylate (ITEMA) and 2‐isothiocyanatoethyl acrylate (ITEA), were synthesized, and their radical polymerizations were examined, respectively. ITEMA and ITEA were synthesized by addition of carbon disulfide to 2‐aminoethyl methacryrate or 2‐aminoethyl acrylate, followed by treatment with ethyl chloroformate. Radical polymerizations of the obtained monomers ( ITEMA , ITEA ) were carried out methyl ethyl ketone using 2,2'‐azobisisobutyronitrile (AIBN) as an initiator to obtain the corresponding polymers. The glass transition temperatures of the poly‐ITEMA and poly‐ITEA were determined to be 55 and 2 °C by differential scanning calorimetry, respectively. The 5 wt % decomposition temperatures of the poly‐ITEMA and poly‐ITEA were determined to be 277 and 269 °C by thermogravimetric analysis, respectively. Isothiocyanato groups in the monomers did not react with water in acetone solution at 60 °C for 24 h to be tolerable to water. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4522–4529     

Sulfonated silica‐based electrolyte nanocomposite membranes

New functionalized particles were prepared by attaching sulfonated aromatic bishydroxy compounds onto fumed silica surface. First, a bromophenyl group was introduced onto the silica surface by reaction of bromophenyltrimethoxysilane with fumed silica. Then, sulfonated bishydroxy aromatic compounds were chemically attached to the silica surface by nucleophilic substitution reactions. The structure of the modified silica was characterized by elemental analysis: ¹³C‐NMR, ²⁹Si‐NMR, and FTIR. Afterward, novel inorganic–organic electrolyte composite membranes based on sulfonated poly(ether ether ketone) have been developed using the sulfonated aromatic bishydroxy compounds chemically attached onto the fumed silica surface. The composite membrane prepared using silica with sulfonated hydroxytelechelic, containing 1,3,4‐oxadiazole units, has higher proton conductivity values in all range of temperatures (40–140 °C) than the membrane containing only the plain electrolyte polymer, while the methanol permeability determined by pervaporation experiment was unchanged. A proton conductivity up to 59 mS cm^?1 at 140 °C was obtained. The combination of these effects may lead to significant improvement in fuel cells (fed with hydrogen or methanol) at temperatures above 100 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2278–2298, 2006     

Polymeric phthalates: Potential nonmigratory macromolecular plasticizers

The synthesis of 4‐vinyl‐1,2‐phthalate esters via Suzuki coupling is described, followed by nitroxide‐mediated polymerization to prepare short homopolymers (degree of polymerization [DP] = 10–40, polydispersity index [PDI] = 1.1–1.3). Random copolymers with n‐butyl acrylate (NBA) were prepared. Copolymers rich in phthalate ester residues of medium lengths (DP = 16–48, PDI = 1.2–1.8) and of shorter lengths (DP = 8–17, PDI = 1.2–1.3) were prepared. Copolymers rich in NBA residues were also prepared (DP = 13–19, PDI = 1.2–1.3). All polymers were oily liquids, with glass transitions temperatures undetected between 75 and ?40 °C, indicating these polymeric phthalates hold promise as potential nonmigratory phthalate plasticizers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013