Polytetrahydrofuran amphiphilic networks. I. Synthesis and characterization of polytetrahydrofuran acrylate ditelechelic and polyacrylamide‐l‐polytetrahydrofuran networks

A series of novel amphiphilic polyacrylamide‐l‐polytetrahydrofuran (PAm‐l‐PTHF) networks were prepared by the free‐radical copolymerization of hydrophobic ditelechelic polytetrahydrofuran acrylate (PTHFDA) with hydrophilic acrylamide. PTHFDA was synthesized by acrylation of the corresponding hydroxycapped PTHF with acrylic acid in cyclohexane. After acrylation, there was no significant difference in the molecular weights and molecular weight distributions between the original PTHF and the resulting PTHFDA. Network structures and compositions were characterized by elemental analyses, Fourier transform infrared, differential scanning calorimetry, scanning electron microscopy, and swelling data. The networks can swell both in organic solvents and in water, which indicates that they are amphiphilic. The swelling of the networks in different solvents is composition‐dependent. According to differential scanning calorimetry, scanning electron microscopy, and swelling tests, the networks have a microphase‐separated and bicontinuous morphology. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3812–3820, 2000     

Polytetrahydrofuran amphiphilic networks. IV. Swelling behavior of poly(acrylic acid)‐l‐polytetrahydrofuran and poly(methacrylic acid)‐l‐polytetrahydrofuran networks

Poly(acrylic acid)‐l‐polytetrahydrofuran (PAA‐l‐PTHF) and poly(methacrylic acid)‐l‐polytetrahydrofuran (PMAA‐l‐PTHF) networks were synthesized by the free‐radical copolymerization of hydrophobic polytetrahydrofuran diacrylates with hydrophilic acrylic acid and methacrylic acid. Their swelling behavior was studied. Both PAA‐l‐PTHF and PMAA‐l‐PTHF networks had four solubility parameters, which indicated that they exhibited not only the properties of both hydrophobic and hydrophilic segments but also the combined properties of these two segments. The swell of these two series of networks was composition‐dependent in organic solvents and water. The relationship between the equilibrium swelling ratio (SR_e) in nonpolar solvents and the composition of the networks [the weight fraction of the PTHF segment (PTHF%)] may be expressed with a linear equation: SR_e = A × PTHF% + B. A and B are parameters that relate to the interaction of hydrophilic and hydrophobic segments with nonpolar solvents and to the properties of the networks, respectively. Because of the presence of a ? COOH group, these two network series were pH‐sensitive when the content of hydrophilic segments was higher. The pH sensitivity of networks could be controlled not only by the composition of the networks but also by the hydrophobic degree of the hydrophilic segments. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1784–1790, 2001     

Synthesis and radical polymerization of methacrylate endowed with bicyclobis(γ‐butyrolactone) moiety through methylene linker

A series of methacrylates bearing bicyclobis(γ‐butyrolactone) (BBL) moiety were synthesized and radically polymerized to afford the corresponding poly(methacrylate)s bearing BBL moiety in the side chain, with expecting that the high polarity and rigidity of BBL would be inherited by the polymers. The resulting polymers were soluble in polar aprotic solvents such as dimethyl sulfoxide and N,N‐dimethylformamide because of the high polarity of the BBL moiety. The glass transition temperatures (T_g) of the polymers depended on the length of methylene linker that tethered the methacrylate and BBL moieties, making the use of shorter linkers lead to higher T_gs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2462–2468     

Synthesis and characterization of a film‐forming,crosslinked, amphiphilic block copolymer of butadiene and acrylamide

An amphiphilic block copolymer of acrylamide and butadiene was synthesized by the polymerization of acrylamide in the presence of the crosslinker N,N′‐methylene bisacrylamide initiated by a hydroxyl‐terminated polybutadiene/V(V) macroredox initiator. The product had good film‐forming ability. It was characterized by IR and NMR spectroscopy, viscosity, swelling, and microhardness measurements, scanning electron micrography, and differential scanning calorimetry. A good film was obtained from the block copolymer with a greater proportion of butadiene; it had greater permeability for nonpolar solvents, and it was poorly permeable to water and other polar solvents. The film swelled in polar and nonpolar solvents and had almost the same capacity for the loading and release of hydrophilic and hydrophobic dyes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3290–3303, 2006     

Microphase‐separated structure of telechelic urethane acrylate anionomers and their network in various solvents

Telechelic urethane acrylate anionomer (UAA) chain showed less viscosity and polyelectrolyte behavior in water than dimethyl acetamide (DMAc) because of hydrophobic aggregation. UAA networks prepared in different solvents (water and DMAc) exhibited very different swelling behaviors in the same swelling medium, which can be interpreted as due to the very different microstructures formed in the solvents. UAA networks prepared with water (UAHG networks) had microphase‐separated hydrophilic and hydrophobic domains, whereas UAA networks synthesized with DMAc (UADG networks) had relatively homogeneous network structures. The mechanical property of the UAHG and UADG networks, measured with a dynamic mechanical analyzer, was also very sensitive to the solvent type used during the crosslinking reaction. UAHG networks with a microphase‐separated structure had a higher modulus than UADG networks. The results of the mechanical property measurements showed that water was a much better solvent for the hydrophilic hard segments of UAA chain than DMAc, even though DMAc dissolved both hydrophilic and hydrophobic segments of UAA chain. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2081–2095, 2000     

Morphology study of Nafion membranes prepared by solutions casting

The structures of Nafion membranes prepared by solutions casting from low aliphatic alcohols/water mixture solvents and N,N′‐dimethyl formamide (DMF) solvent were investigated using differential scanning calorimeter and small angle X‐ray scattering. The aggregation behavior of Nafion molecules in the casting solutions was also investigated using dynamic light scattering. We show that the morphology of membranes was strongly influenced by the conformations of Nafion molecules in the solutions. In aliphatic alcohol/water mixture solvents, which have a worse compatibility with Nafion backbones, the Nafion molecules aggregate and form fringed rod‐like structures. These primary rod‐like structures then aggregate again through fringed side chains to form secondary ionic aggregations. In DMF solvent, owing to its better compatibility with Nafion backbones, less Nafion molecules aggregate. The high degree of Nafion molecular aggregations in aliphatic alcohol/water mixture solvents leads to a high degree of hydrophobic and hydrophilic phase separation for membranes prepared by casting from Nafion/aliphatic alcohol/water solutions. However, the lower degree of molecular aggregations in DMF solvent results in a lower degree of hydrophobic and hydrophilic phase separation for membranes prepared by casting from Nafion/DMF solution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3044–3057, 2005     

Semi‐interpenetrating polymer networks of methyl cellulose and polyacrylamide prepared by frontal polymerization

In this study, the feasibility of frontal polymerization (FP) as an alternative and convenient technique for the preparation of semi‐interpenetrating polymer networks made of methyl cellulose (MC) and cross‐linked polyacrylamide (PAAm) is demonstrated. FP was performed in water and glycerol, as largely available, nontoxic solvents. Although FP occurred in both media, differences were found by comparing the samples made in the two solvents. In particular, those prepared in water are characterized by larger inhomogeneity and less reproducibility, thus accounting for the boiling effects that influence propagating polymerization fronts when water was used. The effects of the ratio among MC and PAAm, the amount of cross‐linker and solvent medium were studied in terms of influence on temperature and velocity of FP fronts, glass transition temperature (dried samples), swelling behavior, dynamic‐mechanical properties (gels swollen in both water or glycerol), and tensile behavior. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1268–1274     

Polyaniline copolymers with solvent‐mimic side chains

We investigated new polyaniline copolymers with solvent‐mimic side chains for enhanced processability in various solvents. The solvent‐mimic side chains, benzyloxypropoxy (BOP), phenoxybutoxy (POB), and dihydroxypropoxy (DHP), were introduced into copolymers and used with nonpolar aromatic and polar alcoholic solvents, respectively. Compared to a polyaniline homopolymer, polyaniline copolymers with a small amount of side chains (<4 mol %) exhibit different physical properties, including film‐forming ability. This can be attributed to the solvent‐mimic side chains strongly interacting with the solvent and/or the polyaniline backbone. Especially, in nonpolar aromatic solvents, polyaniline copolymers with nonpolar aromatic BOP and POB side chains exhibit good film‐forming ability leading to high electrical conductivity, while the polyaniline homopolymer did not form a film. Therefore, introducing solvent‐mimic side chains in conducting polymers is a very attractive method of enhancing their processability and physical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1986–1995     

pH‐ and β‐cyclodextrin‐responsive micelles based on polyaspartamide derivatives as drug carrier

A novel kind of graft polymer poly(aspartic acid)‐ethanediamine‐g‐adamantane/methyloxy polyethylene glycol (Pasp‐EDA‐g‐Ad/mPEG) was designed and synthesized for drug delivery in this study. The chemical structure of the prepared polymer was confirmed by proton NMR. The obtained polymer can self‐assemble into micelles which were stable under a physiological environment and displayed pH‐ and β‐cyclodextrin (β‐CD)‐responsive behaviors because of the acid‐labile benzoic imine linkage and hydrophobic adamantine groups in the side chains of the polymer. The doxorubicin (Dox)‐loaded micelles showed a slow release under physiological conditions and a rapid release after exposure to weakly acidic or β‐CD environment. The in vitro cytotoxicity results suggested that the polymer was good at biocompatibility and could remain Dox biologically active. Hence, the Pasp‐EDA‐g‐Ad/mPEG micelles may be applied as promising controlled drug delivery system for hydrophobic antitumor drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1387–1395     

Thiolactone chemistry for the synthesis of functional silicone‐based amphiphilic co‐networks

A series of amphiphilic co‐networks (ACNs) is prepared in a straightforward way via thiolactone chemistry by crosslinking a multivalent thiolactone‐functional poly(dimethylsiloxane) building block with poly(ethylene glycol) diacrylates. Formation of the networks is triggered by the addition of an amine, of which the nucleophilicity and steric bulk control the curing kinetics. Furthermore, some of the crosslinks can be sacrificed to introduce a fluorescent group or dye via a thia‐Michael addition, without affecting the bulk mechanical properties and swelling capabilities. The obtained ACNs exhibit a unique set of properties because of their nanophase separation, resulting in hydrophilic PEG and hydrophobic PDMS phases. Hence, swelling in both water and organic solvents is observed, of which the extent can be tuned by varying the overall PEG content. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 322–333     

Hydrophobic and hydrophilic aggregation of tailor‐made urethane acrylate anionomers in various solvents and their network structures

Tailor‐made urethane acrylate anionomer (UAA) chains show higher viscosity and polyelectrolyte behavior in dimethyl sulfoxide (DMSO) than in water and toluene. Water is a nonsolvent for the hydrophobic soft segment but a good solvent for the hydrophilic hard segments, so hydrophobic segments are aggregated and form particles in the water phase, resulting in a smaller viscosity. Also, the fact that the viscosity of UAA chains is lowest in toluene can be interpreted as a result of ionic aggregation due to the nonpolarity of toluene. The structures of UAA networks dramatically change with the nature of the solvents used (i.e., the interaction between the UAA chains and the solvents used changes); this is confirmed by the results of tensile property, morphology, and wide‐angle X‐ray scattering data. Ionic aggregation formed in UAA/toluene (UATG networks) and hydrophobic aggregation formed in UAA/water (UAAG networks) are locked in by a chemical crosslinking reaction and result in a greater modulus and X‐ray scattering intensity. The greater elongation and swelling ratio in methylene chloride of UATG networks prepared in a UAA/toluene solution indicates that toluene is a better solvent than DMSO for the hydrophobic segments of UAA chains. Also, the greater swelling ratio in a pH 11 buffer solution and greater modulus of UAAG networks show that water is a better solvent than DMSO for hydrophilic ionic segments. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1903–1916, 2000     

Synthesis of new amphiphilic and lypophilic polymer networks containing 2‐methyl‐ and 2‐nonyl‐2‐oxazoline by the macroinitiator method

New amphiphilic and lypophilic polymer networks were obtained by the copolymerization of 2‐methyl‐2‐oxazoline (MeOXA), and/or 2‐nonyl‐2‐oxazoline (NoOXA) and 2,2′‐tetramethylenebis(2‐oxazoline) (BisOXA), respectively, initiating the copolymerization by random copolymers of chloromethylstyrene and methyl methacrylate or of chloromethylstyrene and styrene (macroinitiator method). Potassium iodide was used as an activator agent and the reaction was carried out in benzonitrile at 110 °C. In general, the polymer gels were obtained with a yield of 62 to 88%. The networks were characterized by high‐resolution magic angle spinning (HRMAS) NMR spectroscopy and by its absorption of polar and nonpolar solvents. In the case of amphiphilic polymer networks, the absorption of solvents depends on the molar ratio of 2‐methyl‐ to 2‐nonyl‐2‐oxazoline inside the polymer network favoring the absorption of polar solvents with a higher content of 2‐methyl‐2‐oxazoline. These gels showed a maximal swelling degree of 13 mL of water, 20 mL of methanol, and 13 mL of chloroform, respectively, per g of polymer. The lypophilic polymer networks containing only 2‐nonyl‐2‐oxazoline showed a maximal swelling degree of 8 mL of toluene, 14 mL of chloroform, and 2 mL of methanol, respectively, per g of the lypophilic network. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 122–128, 2005     

Synthesis and liquid crystalline behavior of bulky poly(methacrylamide)s

N‐(Bis(4‐(2‐ethylhexyloxy)phenyl)(phenyl)‐methyl)methacrylamide was synthesized and polymerized via reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. The chain‐transfer agent (4‐cyano‐4‐(phenylcarbonothioylthio) pentanoic acid (CPADB)), combined with a chiral additive, and a radical initiator yielded polymers with dispersities between 1.2 and 1.4. At low concentrations, the polymers are soluble in hexanes and chloroform while at higher concentrations they swell in these solvents. Characterization of the polymers by wide‐angle X‐ray scattering (WAXS) revealed an interplanar distance of 19.0 Å. The WAXS data combined with polarized optical microscopy support a lamellar crystallization and lyotropic liquid crystalline behavior in hexanes and chloroform. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2563–2568     

A visible light responsive azobenzene‐functionalized polymer: Synthesis,self‐assembly,and photoresponsive properties

A novel visible light responsive random copolymer consisting of hydrophobic azobenzene‐containing acrylate units and hydrophilic acrylic acid units has been prepared. The azobenzene molecule bearing methoxy groups at all four ortho positions is readily synthesized by one‐step conversion of diazotization. The as‐prepared polymer can self‐assemble into nanoparticles in water due to its amphiphilic nature. The tetra‐o‐methoxy‐substituted azobenzene‐functionalized polymer can exhibit the trans‐to‐cis photoswitching under the irradiation with green light of 520 nm and the cis‐to‐trans photoswitching under the irradiation with blue light of 420 nm in both solution and aggregate state. The morphologies of the self‐assembled nanoparticles are revealed by TEM and DLS. The controlled release of loaded molecules from the nanoparticles can be realized by adjusting pH value since the copolymer possesses pH responsive acrylic acid groups. The fluorescence of loaded Nile Red in the nanoparticles can be tuned upon the visible light irradiation. The reversible photoswitching of the azobenzene‐functionalized polymer under visible light may endow the polymer with wide applications without using ultraviolet light at all. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2768–2775     

Ambient‐temperature copper‐catalyzed atom transfer radical polymerization of methacrylates in ethylene glycol solvents

The use of ethylene glycol solvents in the room‐temperature atom transfer radical polymerization (ATRP) of various hydrophobic and hydrophilic methacrylates is demonstrated. Unlike many of the very polar solvents described in the literature for room‐temperature ATRP, these solvents have good solvency for a wide range of polymers and monomers and are cheap and relatively nontoxic. Ethylene glycols with one hydroxyl and one methoxy group, such as tri(ethylene glycol) monomethyl ether (TEGMME), provide optimal results. The polymerization of methyl methacrylate in TEGMME with CuBr/N,N,N′N′,N″‐pentamethyldiethylenetriamine as the catalyst requires the addition of CuCl₂ at the beginning of the reaction to produce well‐controlled polymerizations. This leads to polymers with predictable molecular weights and relatively narrow polydispersities. Polymerization in solvents that are fully methoxy‐capped terminate prematurely because of catalyst precipitation. The electrochemical behavior of copper complexes in selected solvents is examined to determine why these solvents provide good rates at room temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1588–1598, 2005     

Solvophobic Acceleration of a Diels–Alder Reaction in True Solutions in Organic Solvents

The rate of Diels–Alder reaction of diene 9,10‐bis(hydroxymethyl)anthracene with dienophile N‐ethylmaleimide was studied in a series of solvents with different polarity and hydrogen‐bonding ability. Enthalpies and entropies of activation were determined from the temperature dependences of the rate constants. Rate acceleration in nonaqueous protic solvents such as glycerol, propylene, and ethylene glycols was observed. In addition, enthalpy versus entropy of activation plots show a compensation pattern different from the other considered solvents, which can be linked with the solvophobic effects observed in polyhydric alcohols. However, the solvophobic acceleration was not as strong as the hydrophobic acceleration in water. Hydrogen bonding of the reactants and transition state with solvent also influences the reaction rate. The studied reaction is slightly promoted in hydrocarbon solvents in comparison with aprotic polar solvents. This was explained by hydrogen bonding of the hydroxyl groups of diene with dienophile in transition state, which requires prior breaking of the hydrogen bonds of these groups with polar solvent molecules.     

Synthesis of well‐defined star‐shaped poly(ε‐caprolactone)/poly(ethylbene glycol) amphiphilic conetworks by combination of ring opening polymerization and “click” chemistry

Well‐defined star‐shaped hydrophobic poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) amphiphilic conetworks (APCNs) have been synthesized via the combination of ring opening polymerization (ROP) and click chemistry. Alkyne‐terminated six arm star‐shaped PCL (6‐s‐PCLx‐C?CH) and azido‐terminated PEG (N₃‐PEG‐N₃) are characterized by ¹H NMR and FT‐IR. The swelling degree of the APCNs is determined both in water and organic solvent. This unique property of the conetworks is dependent on the nanophase separation of hydrophilic and hydrophobic phases. The morphology and thermal behaviors of the APCNs are investigated by SEM and DSC respectively. The biocompatibility is determined by water soluble tetrazolium salt reagents (WST‐1) assay, which shows the new polymer networks had good biocompatibility. Through in vitro release of paclitaxel (PTX) and doxorubicin (DOX), the APCNs is confirmed to be promising drug depot materials for sustained hydrophobic and hydrophilic drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 407–417     

Convex solubility parameters for polymers

Solubility parameters are certain measurable quantities that are observed to influence the ability of a solvent to fully dissolve a polymer. Current theory partitions the intermolecular forces between dispersion, polar, and hydrogen bonding interactions, thereby generating a three‐dimensional solubility parameter space. The Hansen solubility parameters of a polymer are taken to be the center of a sphere obtained from the best fit of the coordinates of good solvents in the parameter space. Investigations of several polymers (lignin, polyethersulfone, and bitumen) show that the convex hull of all known good solvents in the three‐dimensional parameter space also gives a meaningful interpretation of the solubility region. Several methods for computing the convex solubility parameters of a polymer from the convex solubility region are described. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1089–1097     

Synthesis and characterization of hyperbranched amphiphilic block copolymers prepared via self‐condensing RAFT polymerization

Four families of hyperbranched amphiphilic block copolymers of styrene (Sty, less polar monomer) and 2‐vinylpyridine (2VPy, one of the two more polar monomers) or 4‐vinylpyridine (4VPy, the other polar monomer) were prepared via self‐condensing vinyl reversible addition‐fragmentation chain transfer polymerization (SCVP‐RAFT). Two families contained 4VPy as the more polar monomer, one of which possessing a Sty‐b‐4VPy architecture, and the other possessing the reverse block architecture. The other two families bore 2VPy as the more polar monomer and had either a 2VPy‐b‐Sty or a Sty‐b‐2VPy architecture. Characterization of the hyperbranched block copolymers in terms of their molecular weights and compositions indicated better control when the VPy monomers were polymerized first. Control over the molecular weights of the hyperbranched copolymers was also confirmed with the aminolysis of the dithioester moiety at the branching points to produce linear polymers with number‐average molecular weights slightly greater than the theoretically expected ones, due to recombination of the resulting thiol‐terminated linear polymers. The amphiphilicity of the hyperbranched copolymers led to their self‐assembly in selective solvents, which was probed using atomic force microscopy and dynamic light scattering, which indicated the formation of large spherical micelles of uniform diameter. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1310–1319     

Facile fabrication of fast recyclable and multiple self‐healing epoxy materials through diels‐alder adduct cross‐linker

A reversibly cross‐linked epoxy resin with efficient reprocessing and intrinsic self‐healing was prepared from a diamine Diels‐Alder (DA) adduct cross‐linker and a commercial epoxy oligomer. The newly synthesized diamine cross‐linker, comprising a DA adduct of furan and maleimide moieties, can cure epoxy monomer/oligomer with thermal reversibility. The reversible transition between cross‐linked state and linear architecture endows the cured epoxy with rapid recyclability and repeated healability. The reversibly cross‐linked epoxy fundamentally behaves as typical thermosets at ambient conditions yet can be fast reprocessed at elevated temperature like thermoplastics. As a potential reversible adhesive, the epoxy polymer with adhesive strength values about 3 MPa showed full recovery after repeated fracture‐thermal healing processes. The methodology explored in this contribution provides new insights in modification of conventional engineering plastics as functional materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2094–2103