An ambient self‐curable latex based on colloidal dispersions in water of two functionalized polymers and the thermally reversible crosslinked films generated

An ambient self‐curable latex (ASCL) was prepared by mixing colloidal dispersions in water of a chloromethylstyrene (CMS)‐functionalized polymer and a tertiary‐amine‐functionalized polymer. The two dispersions were obtained via the conventional emulsion copolymerization of CMS and 2‐(dimethylamino)ethylacrylate (DMAEA), respectively, with styrene (St), butyl acrylate (BA), or both. No visible coagulation was observed either in the blends after 6 months of storage or after the latexes were introduced into aqueous media with pHs in the range of 3–11. Continuous, transparent, crosslinked elastic films with smooth surfaces were obtained via casting and drying the ASCL at room temperature, when one or both of the two functional polymer particles contained BA monomeric units. Thermocompression cycles; swelling experiments; solubility tests; and ¹H NMR, IR, DSC, and transmission electron microscopy tests were carried out to investigate the crosslinking and morphology of the films. The following observations were made: (1) the crosslinks in the films were generated via the Menschutkin reaction (quaternization) between the  CH₂‐Cl groups of the CMS containing particles and the amine groups of the DMAEA containing particles; (2) the crosslinked films were thermally remoldable due to reversible decrosslinking (dequaternization) on heating and recrosslinking (requaternization) on cooling; and (3) phase separation in the films was observed when one of the functional polymers (for instance, the nonpolar CMS‐St copolymer) was incompatible with the other one (for instance, the polar BA‐DMAEA copolymer). The present ASCL might be useful in producing water‐borne coatings and adhesives, elastic films, and functional membranes. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 389–397, 2001     

Long‐term stability of an ambient self‐curable latex based on colloidal dispersions in water of two reactive polymers

An ambient self‐curable latex (ASCL) was prepared via the blending of colloidal dispersions in water of a chloromethylstyrene‐functionalized copolymer and a tertiary‐amine‐functionalized copolymer. Upon casting and drying under ambient conditions, the ASCL could generate crosslinked continuous polymer films. The crosslinking occurred via the Menschutkin reaction (quaternization) between the two types of functional groups. Because this reaction was reversible at high temperatures, the films could be decrosslinked and hence were self‐curable. The prepared ASCL exhibited excellent colloidal and chemical stability during long‐term storage: no significant changes in the colloidal properties, such as the particle size, electrophoretic mobility, and crosslinking reactivity, were observed after 48 months of storage. The electrophoretic measurements indicated that the electrostatic repulsion between the negatively charged particles of the ASCL was responsible for the excellent stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2598–2605, 2005     

Thermally reversible linking of halide-containing polymers by potassium dicyclopentadienedicarboxylate

A novel crosslinker for thermally reversible covalent (TRC) linking of halide-containing polymers is suggested. Chlorine-containing polymers such as chloromethylstyrene copolymers, chlorinated polypropylene, polyvinylchloride, chlorinated polyisoprene, and polyepichlorohydrin were crosslinked with potassium dicyclopentadienedicarboxylate (KDCPDCA). The crosslinker was prepared by reacting potassium ethoxide with dicyclopentadienedicarboxylic acid. Because of the low solubility of KDCPDCA in organic solvents, a phase transfer catalyst, benzyltrimethyl-ammonium bromide, was employed for the crosslinking reaction. The crosslinking reaction occurred at a higher rate in a polar solvent, such as dimethylformamide, than in a nonpolar one, such as toluene, and was affected by the nature of the chlorine-containing polymer. Some of the polymers crosslinked even at room temperature. The chain-extending reaction between KDCPDCA and a α,ω-dihalide compound such as α,α′-dichloro-p-xylene, 1,4-dichlorobutane, or 1,4-dibromobutane also was carried out to obtain linear oligomers. The IR spectra indicated that the crosslinking and chain-extending reactions were based on the esterification between the halide carbon bonds of the polymer and the COOK groups of KDCPDCA. The flowability at 195 °C and solubility on heating in a dichlorobenzen-maleic compound mixture of the crosslinked polymers indicated that the TRC crosslinking occurred via the reversible Diels–Alder cyclopentadiene/dicyclopentadiene conversion as long as the polymer was thermally stable and did not contain olefinic CC bonds. The TRC linking also was confirmed by the rapid decrease of the specific viscosity of the obtained linear oligomers on heating. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4390–4401, 1999     

Crosslinking of chlorine‐containing polymers by dicyclopentadiene dicarboxylic salts

Alkali‐ and alkali‐earth‐metal salts of dicyclopentadiene dicarboxylic acid (DCPDCA) were prepared and employed as crosslinkers for chlorine‐containing polymers such as polychloromethylstyrene (PCMS), chlorinated polypropylene (CPP), polyepichlorohydrin (PECH), and poly(vinyl chloride) (PVC). Thermally reversible covalent crosslinks (i.e.,  DCPD bridges) between polymer chains were generated through esterification between the chlorine–carbon bonds of the polymer and the carboxylic salt groups of the crosslinker. The crosslinking reactivity decreased in the following sequence: K > Na > LiDCPDCA > alkali‐earth‐metal salts of DCPDCA. In addition, PCMS and CPP had higher gelation rates than PECH and PVC. Good flowability at about 195 °C and solubility in maleimide‐containing dichlorobenzene on heating indicated that the crosslinked PCMS and CPP exhibited thermally reversible crosslinking because of dimer/monomer (cyclopentadiene) conversion of  DCPD moieties via reversible Diels–Alder cycloaddition. Samples of PECH and PVC crosslinked by the alkali salts of DCPDCA were insoluble even when heated in maleimide‐containing dichlorobenzene. However, these crosslinked polymers could be dissolved partially after the same treatment when the crosslinker was an alkali‐earth‐metal salt of DCPDCA. Thermal degradation such as dehydrochlorination of the PECH and PVC might have been responsible for uncontrolled crosslinking because these two polymers are known to be thermally unstable. The unreacted COOK, COONa, or COOLi of the crosslinkers might have initiated base‐induced dehydrochlorination when PECH and PVC were heated at high temperatures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 818–825, 2000     

Synthesis and characterization of saccharide‐based latex particles

The synthesis of new polymer colloids based on renewable resources, such as sugar‐derived monomers, is nowadays a matter of interest. These new polymeric particles should be useful in biomedical applications, such as drug delivery, because of their assumed biodegradability. In this work, two new families of polymer latex particles, based on a sugar‐derived monomer, 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (3‐MDG), were produced and characterized. The syntheses of poly(3‐MDG) crosslinked particles and those obtained by copolymerization with methacrylic acid (MAA), poly(3‐MDG‐co‐MAA) crosslinked particles, were prepared by surfactant‐free emulsion polymerization in a batch reactor. The average particle diameter evolutions, the effect of pH of the dispersion medium on the final average diameters, together with the microscopic and morphological analysis of the particle's surface and inner dominium, were analyzed. Poly(3‐MDG‐co‐EGDMA) stable particles were obtained by adding low amounts of initiator. The surface‐charge density of these particles corresponded to the sulfate groups coming from the initiator. In the second family of latices, poly(3‐MDG‐co‐MAA‐co‐EGDMA) particles, DCP measurements and SEM and TEM observations showed that the sizes and surface characteristics depended on the amounts of MAA and crosslinker used in the reaction mixture. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 443–457, 2006     

Degradable polymer networks and star polymers based on mixtures of two cleavable dimethacrylate crosslinkers: Synthesis,characterization, and degradation

Mixtures of two cleavable dimethacrylate crosslinkers, the hydrolyzable di(methacryloyloxy‐1‐ethoxy)methane (DMOEM) and the thermolyzable 1,1‐ethylenediol dimethacrylate (EDDMA), were used for the preparation of neat crosslinker polymer networks, randomly crosslinked polymer networks of methyl methacrylate (MMA), and star polymers of MMA, using group transfer polymerization in tetrahydrofuran (THF). All star polymers and randomly crosslinked polymer networks containing mixtures of the hydrolyzable DMOEM and the thermolyzable EDDMA crosslinkers gave THF‐soluble final products when subjected to sequential thermolysis and hydrolysis, in this order. When applying sequential hydrolysis and thermolysis, only the star polymers with an EDDMA crosslinker content equal to or higher than 50% gave THF‐soluble final products. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5853–5870, 2009     

Core–shell nanogels by RAFT crosslinking polymerization: Synthesis and characterization

A synthetic methodology is described for the preparation of core–shell nanogels by reversible addition‐fragmentation chain transfer. Well‐defined macro chain transfer agents (macro‐CTA's) were prepared in a first step using monomers that yield sensitive polymers. In the second step, a crosslinker alone or with the addition of a functionalized comonomer were used to form a crosslinked core. The ratio of crosslinker to macro‐CTA is crucial to yield nanogels. Furthermore, the polymerization time has an impact in the architecture of the nanomaterial obtained: it evolves from a core‐crosslinked star to a core–shell nanogel. Controlling the molecular weight of the macro‐CTA and the type of comonomer in the core forming step, core–shell nanogels with hydrodynamic diameters from 22 to 168 nm and a core that represents from 35 to 77% of the size, were prepared containing functional groups in the core which could be used as catalytic scaffolds. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.     

Crosslinkable polyurethane bearing a methacrylate structure in the side chain

A polyurethane bearing methacrylate groups through urethane linkages was prepared by the addition of 2‐methacryloyloxyethyl isocyanate to the hydroxyl groups in poly(hydroxyurethane) prepared by the polyaddition of a bifunctional cyclic carbonate with 1,12‐diaminododecane. The urethanization proceeded quantitatively in the presence of a catalytic amount of di‐n‐butyltin dilaurate at an ambient temperature, whereas a crosslinked product was obtained from the reaction at 60 °C. The resulting linear polyurethane, bearing a methacrylate structure, was thermally crosslinkable. Its radical copolymerization with vinyl‐type monomers afforded the corresponding crosslinked polymers, whose low glass transition temperatures suggested the flexibility of the polymer chains in the crosslinked product. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3400–3407, 2007     

Synthesis and properties of methacrylate‐based networked polymers having ionic liquid structures

Methacrylate‐based networked polymers having ionic liquid structures were prepared by radical copolymerization of methyl methacrylate (MMA) with multifunctional crosslinkers: ethyleneglycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), or triethyleneglycol dimethacrylate (TEGDMA), in the presence of 1‐ethyl‐3‐methylethyl‐1‐imidazolium bis(trifluoromethane)sulfonyl imide (EMImTFSI). The fundamental physical properties of several film samples prepared by varying the monomer composition and ionic liquid content were investigated. The obtained materials became turbid with increasing crosslinker content and ionic liquid content. Their ionic conductivity increased with increasing ionic liquid content, while it was almost independent of the crosslinker content. EGDMA‐derived materials and TMPTMA‐derived materials showed higher ionic conductivity than TEGDMA‐derived materials. TMPTMA‐derived materials showed higher thermal stability than EGDMA or TEGDMA‐derived materials. EGDMA and TMPTMA‐derived materials were stiffer than the TEGDMA‐derived materials. The elastic modulus of the film samples increased but the film became more brittle with the increase of crosslinker content. Scanning electron microscopy and atomic force microscopy observation revealed that phase separation of networked polymers and ionic liquid occurred in the highly crosslinked samples, and the phase separation structures became larger in scale with the increase of crosslinking density. This phase separation was considered to have a strong effect on the mechanical properties of the film samples. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Polymer coating of carboxylic acid functionalized multiwalled carbon nanotubes via reversible addition‐fragmentation chain transfer mediated emulsion polymerization

In this work, successful polymer coating of COOH‐functionalized multiwalled carbon nanotubes (MWCNTs) via reversible addition fragmentation chain transfer (RAFT) mediated emulsion polymerization is reported. The method used amphiphilic macro‐RAFT copolymers as stabilizers for MWCNT dispersions, followed by their subsequent coating with poly(methyl methacrylate‐co‐butyl acrylate). Poly(allylamine hydrochloride) was initially used to change the charge on the surface of the MWCNTs to facilitate adsorption of negatively charged macro‐RAFT copolymer onto their surface via electrostatic interactions. After polymerization, the resultant latex was found to contain uniform polymer‐coated MWCNTs where polymer layer thickness could be controlled by the amount of monomer fed into the reaction. The polymer‐coated MWCNTs were demonstrated to be dispersible in both polar and nonpolar solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Amphiphilic polymethacrylates as crosslinked polymer precursors obtained by free‐radical monomethacrylate/dimethacrylate copolymerizations

As an extension of our work on the elucidation of the mechanism and control of 3‐dimensional network formation in the free‐radical crosslinking polymerization and copolymerization of multivinyl compounds with the aim to molecularly design vinyl‐type network polymers, novel amphiphilic polymers were prepared as crosslinked polymer precursors. Thus, benzyl methacrylate, a nonpolar monomer, was copolymerized radically with 5 mol % of triicosaethylene glycol dimethacrylate [CH₂C(CH₃)CO(OCH₂CH₂)₂₃OCOC(CH₃)CH₂], a polar monomer, in the presence of lauryl mercaptan as a chain transfer agent. The resulting prepolymers (i.e., vinyl‐type network‐polymer precursors or amphiphilic polymers) were characterized mainly by viscometry using t‐butylbenzene (t‐BB) and a t‐BB/MeOH (80/20) mixture as solvents. The viscosities in the t‐BB/MeOH (80/20) mixture were quite high compared with those in t‐BB, and completely reversed concentration dependencies were observed in the solvents. These are discussed by considering the difference in conformation and the shrinkage of polar, flexible polyoxyethylene units or the entanglement of nonpolar, rigid primary chains. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4396–4402, 2000     

Impact of poly(ɛ‐caprolactone) architecture on the thermomechanical and shape memory properties

We report the synthesis of linear‐ and brush‐type poly(?‐caprolactone) (PCL) networks and investigate their thermal, mechanical, and shape memory behavior. Brush‐PCLs are prepared by ring‐opening metathesis polymerization (ROMP) of a norbornenyl‐functionalized ?‐caprolactone macromonomer (MM‐PCL) of different molecular weights. The linear analog, diacrylate end‐functionalized PCL (linear‐PCL), having comparable molecular weight of side chain of brush‐PCL is also synthesized. These polymers are thermally cured by a radical initiator in the presence of poly(ethylene glycol) diacrylate crosslinker. Thermal and linear viscoelastic properties as well as shape memory performance of the resulting PCL networks are investigated, and are significantly impacted by the PCL architecture. Therefore, our work highlights that tailoring macromolecular architecture is useful strategy to manipulate thermal, mechanical, and resulting shape memory properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3424–3433     

Particle and breath figure formation of triblock copolymers having self‐complementary hydrogen‐bonding units

Novel triblock copolymers having self‐complementary hydrogen‐bonding units were synthesized by using reversible addition–fragmentation transfer polymerization. As characterized by dynamic light scattering and atomic force microscopy, these polymers formed noncovalently crosslinked polymer particles and showed an aggregation behavior by intermolecular and intramolecular interactions. At low concentration, polymers formed nanoparticles, and the particle diameter increased with increasing polymer concentration. Well‐ordered hexagonal microstructures were prepared by “Breath Figure” technique with the triblock copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Sustainable self‐healing elastomers with thermoreversible network derived from biomass via emulsion polymerization

Motivated by the growing demand for greener and sustainable polymer systems, self‐healing elastomers were prepared by emulsion polymerization of terpene and furfural‐based monomers. Both the method and the monomers were green and sustainable. The synthesized copolymers showed molecular weights between 59,080 and 84,210 Da and glass‐transition temperature (T_g) between ?25 and ?40 °C, implying rubbery properties. A set of one‐dimensional (1D) and two‐dimensional (2D) NMR spectroscopy supported the formation of the copolymer and nuclear spin–spin coupling in the copolymer. Reactivity ratios were determined by conventional linear method. A thermoreversible network was achieved for the first time by reacting the furan‐based polymer with bismaleimide (BM) as a crosslinker, via a Diels?Alder (DA) coupling reaction. The reversible nature of the polymer network was evidenced from infrared and NMR spectroscopy. The thermoreversible character of the DA crosslinked adduct was confirmed by applying retro‐DA reaction (observed in differential scanning calorimeter [DSC] analysis) and mechanical recovery was verified by repeated heating and cooling cycles. The network polymers displayed excellent self‐healing ability, triggered by heating at 130 °C for 4–12 h, when their scratched surface was screened by microscopic visualization. The healing efficiency of the crosslinked DA‐adduct was calculated as 78%, using atomic force microscopy. This work provides a green and efficient approach to prepare new green and functional materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 738–751     

“Continuous” emulsifier‐free emulsion polymerization for the synthesis of monodisperse polymeric latex particles

A “continuous” emulsifier‐free emulsion copolymerization (CEFEP) of styrene and divinylbenzene (DVB) or methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) has been devised to produce uniform polymeric microspheres of narrow size distribution from 74 nm to 2 μm, depending on reaction time. Monomer and crosslinker vapors were fed continuously into a small reactor. We suggest that after initial nucleation, subsequent CEFEP proceeds near the surfaces of growing particles in a monomer‐swollen outer shell. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3181–3187, 2000     

Phenylboronate‐diol crosslinked polymer/SWCNT hybrid gels with reversible sol–gel transition

This work demonstrates the successful incorporation of functionalized single‐walled carbon nanotubes (f‐SWCNTs) into the phenylboronate‐diol crosslinked polymer gel to create a hybrid system with reversible sol–gel transition. The phenylboronic acid‐containing and diol‐containing polymers were first separately prepared by the reversible addition–fragmentation chain transfer polymerization. Covalent functionalization of single‐walled carbon nanotubes (SWCNTs) with an azide‐derivatized, diol‐containing polymer was then accomplished by a nitrene addition reaction. Subsequently, the hybrid gels were prepared by crosslinking the mixture of f‐SWCNTs and diol‐containing polymer with the phenylboronic acid‐containing polymer. The hybrid gel has been characterized by scanning electron microscopy (SEM) and rheological analysis. The SEM measurement demonstrated a homogeneous dispersion of f‐SWCNTs within the gel matrices. Rheological experiments also demonstrated that the hybrid gel exhibited storage moduli significantly higher than those of the native gel obtained from the phenylboronic acid‐containing and diol‐containing polymers. The hybrid gel can be switched into their starting polymer (f‐SWCNTs) solutions by adjusting the pH of the system. Moreover, the hybrid gel revealed a self‐healing property that occurred autonomously without any outside intervention. By employing this dynamic character, it is possible to regenerate the used gel, and thus, it has the potential to perform in a range of dynamic or bioresponsive applications Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of thermally degradable epoxy adhesives

We have developed a new strategy for the synthesis of epoxide‐containing polymers where the pendant reactive groups are connected to the main backbone via thermally labile oxonorbornene groups. The polymers were synthesized by radical 1,4‐polymerization of the appropriate bicyclic diene monomer. The produced polymers can be crosslinked in the presence of a diamine and de‐crosslinked by thermal treatment at 160 °C, which induces retro‐Diels–Alder reaction and cleaves pendant groups from the polymer backbone, as confirmed by differential scanning calorimetry. The potential for the utilization of this polymer as a thermally removable adhesive was demonstrated by a simple adhesion test. This method provides access to thermally cleavable epoxy networks that can be quickly and irreversibly disintegrated into nonvolatile components upon heating to a specified temperature. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4992–4997     

Lignin,a biomass crosslinker,in a shape memory polycaprolactone network

This work reports a new direction of natural lignin valorization, which utilizes lignin to produce crosslinked polycaprolactone (PCL) via a straightforward synthesis. Lignin's hydroxyl groups of its multibranched phenolic structure allow lignin to serve as crosslinkers, whereas the aromatic groups serve as hard segments. The modified natural lignin containing alkene terminals is crosslinked with a thiol‐terminal PCL via Ru‐catalyzed photoredox thiol‐ene reaction. The high rate of gel contents measured for all crosslinked polymers, with the least being 84% of gel content, indicates efficient crosslinking. The prepared flat rectangular shape lignin‐crosslinked PCL sample demonstrates rapid thermal responsive shape memory behavior at 10 °C and 80 °C showing interconversion between a permanent and temporary shape. The melting temperature of the lignin‐crosslinked PCL is tunable by varying the percent weight of lignin. The 11, 21, and 30 wt % lignin demonstrated T_m of 42 °C, 35 °C, and 26 °C, respectively. The role of lignin as a crosslinker presented in this work suggests that lignin can serve as an efficient biomass‐based functional additive to polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2121–2130     

Polymer coating of graphene oxide via reversible addition–fragmentation chain transfer mediated emulsion polymerization

This work describes a versatile method to encapsulate graphene oxide (GO) with polymers using reversible addition‐fragmentation chain transfer (RAFT) mediated emulsion polymerization. A living low molecular weight anionic macro‐RAFT statistical copolymer of sodium styrene sulfonate, acrylic acid, and butyl acrylate (BA) was synthesized using 2‐{[(butylsulfanyl)carbonothioyl] sulfanyl} propanoic acid as the chain transfer agent. GO was dispersed in water by pretreating the surface with poly(allylamine hydrochloride) (PAH), before being stabilized by the addition of the anionic macro‐RAFT copolymer. PAH was used to facilitate the adsorption of the macro‐RAFT copolymer to the GO surface via electrostatic attraction between opposite charges. The dispersed GO sheets were encapsulated with polymer by the free radical emulsion polymerization of methyl methacrylate and BA under starved fed conditions. The polymer shells encapsulating the GO sheets were formed by the chain extension of the adsorbed living macro‐RAFT copolymer. TEM, SEM, FTIR, and AFM were used to confirm the presence of the polymer layer on the surface of the GO. The thickness of the polymer coating can be adjusted by controlling the amount of monomer fed into the system. Partial polymer coatings of the GO could be achieved by varying the amount of PAH. The encapsulated GO was found to be easily dispersed in both aqueous and organic solvents over a range of polarities. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1413–1421     

Composition control of copolymer in semibatch emulsion copolymerization. II. MMA/styrene/BMA three‐component system

In this study, polymers of the MMA/Styrene/BMA three‐component system were synthesized through either soapless semibatch emulsion copolymerization or soapless batch emulsion copolymerization technique. The optimal monomer feed flow rate was determined from the interphase partition laws, monomer reactivity ratios, and three or four times of iterative experimental procedures through semibatch emulsion copolymerization. As a result, the instantaneous composition of polymers could also be effectively controlled to get the desired final products. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3253–3269, 2000