UV-curable poly(ethylene glycol)–based polyurethane acrylate hydrogel

Poly(ethylene glycol) (PEG) with molecular weight (M_n) of 1000, 2000, 3000, and 4000 g/mol, four types of diisocyanate [hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI), isophorone diisocyanate (IPDI), and toluene diisocyanate (TDI)], two types of comonomers [acrylamide (AAm) and acrylic acid (AAc)] that comprised up to 60% of the total solid were used to prepare UV-curable PEG–based polyurethane (PU) acrylate hydrogel. The gels were evaluated in terms of mechanical properties, water content as a function of immersion time and pH, and X-ray diffraction profiles of dry and swollen films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2703–2709, 1999     

Synthesis and characterization of polyurethane–urea nanoparticles containing methylenedi‐p‐phenyl diisocyanate and isophorone diisocyanate

Water‐based polyurethane–urea (WPUU) nanoparticles containing 4,4′‐methylenedi‐p‐phenyl diisocyanate (MDI) and isophorone diisocyanate (IPDI) were synthesized by a stepwise prepolymer mixing process, that is, the consecutive formation of hydroxyl‐terminated and isocyanate‐terminated polyurethane prepolymers. The reaction behavior, chemical structure, and consequent morphology of the polyurethane prepolymers and WPUU were investigated with Fourier transform infrared (FTIR), gel permeation chromatography, and NMR techniques with MDI concentrations ranging from 0 (pure IPDI) to 50% with respect to the total moles of isocyanate. Wide‐angle X‐ray diffraction and differential scanning calorimetry patterns showed that the crystallinity of WPUU, which mostly originated from crystallizable poly(tetramethylene adipate) polyol, was significantly affected by the MDI content. Both the crystallinity and melting temperature of WPUU decreased as the MDI content increased. Deconvoluted relative peak areas of the carbonyl region in the FTIR spectrum revealed that the effect of hydrogen bonding among the hard segments became favorable as the MDI content increased, whereas the hydrogen bonding of the soft segments significantly decreased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4353–4369, 2004     

Biodegradable aliphatic thermoplastic polyurethane based on poly(ε‐caprolactone) and L‐lysine diisocyanate

A biodegradable aliphatic thermoplastic polyurethane based on L ‐lysine diisocyanate and 1,4‐butanediol hard block segments, and 2000 g/mol poly(ε‐caprolactone) diol soft block segments was synthesized. The resulting polymer was a tough thermoplastic with ultimate tensile strength of 33 MPa and elongation of 1000%. The polymer displayed classic segmented thermoplastic elastomer morphology with distinct hard block and soft block phases. Thermal and dynamic mechanical analyses determined that the material has a useful service temperature range of around ?40 °C to +40 °C, making it an excellent candidate for low‐temperature elastomer and film applications, and potentially as a material for use in temporary orthopedic implant devices. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2990–3000, 2006     

Block and random copolymerization of ε‐caprolactone,L‐, and rac‐lactide using titanium complex derived from aminodiol ligand

A series of di‐ and triblock copolymers [poly(L ‐lactide‐b‐ε‐caprolactone), poly(D,L ‐lactide‐b‐ε‐caprolactone), poly(ε‐caprolactone‐b‐L ‐lactide), and poly(ε‐caprolactone‐b‐L ‐lactide‐b‐ε‐caprolactone)] have been synthesized successfully by sequential ring‐opening polymerization of ε‐caprolactone (ε‐CL) and lactide (LA) either by initiating PCL block growth with living PLA chain end or vice versa using titanium complexes supported by aminodiol ligands as initiators. Poly(trimethylene carbonate‐b‐ε‐caprolactone) was also prepared. A series of random copolymers with different comonomer composition were also synthesized in solution and bulk of ε‐CL and D,L ‐lactide. The chemical composition and microstructure of the copolymers suggest a random distribution with short average sequence length of both the LA and ε‐CL. Transesterification reactions played a key role in the redistribution of monomer sequence and the chain microstructures. Differential scanning calorimetry analysis of the copolymer also evidenced the random structure of the copolymer with a unique T_g. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

FTIR STUDIES ON THE MODEL POLYURETHANE HARD SEGMENTS BASED ON A NEW WATERBORNE CHAIN EXTENDER DIMETHYLOL BUTANOIC ACID （DMBA）

Three model polyurethane hard segments based on dimethylol butanoic acid (DMBA) and 1,6-hexane diisocyanate (HDI), toluene diisocyanate (TDI) and 4,4‘-diphenylmethane diisocyanate (MDI) were prepared by the solution method.Fourier Infrared (FTIR) spectroscopy was employed to study the H-bonds in these model polyurethanes. The model polyurethane hard segment prepared from HDI and 1,4-butanodiol (BDO) was used for comparison. It was found that the incorporation of the pendent carboxyl through DMBA into the model hard segments weakens the original NH…O=C H-bond but gives more H-bond patterns based on the two H-bond donors, urethane NH and carboxylic OH. The carboxylic dimer is one of the main H-bond types and is stronger than another main H-bond type NH…O=C. In addition, the H-bond in aromatic model hard segments is stronger than that of aliphatic hard segments. The appearance of the free C:O and the fact that almost all N-H is H-bonded suggest that there possibly exist either the third H-bond acceptor or the H-bond formed by one acceptor with two donors.     

Reactivity of urethanes at high temperature: Transurethanization and side reactions

The reactivity of urethanes based on 1,6‐hexamethylene diisocyanate (HDI) and 4,4′‐methylene diphenyl diisocyanate (MDI) was investigated at temperatures between 190 °C and 235 °C. Diurethane model compounds end‐capped with either 1‐dodecanol (D‐core‐D) or 1‐hexadecanol (H‐core‐H) were mixed and annealed at high temperature. The core was either MDI or HDI. The transurethanization reaction was followed based on the formation of the compounds (H‐core‐D). The amount of H‐core‐D and of side products, which had formed after variable annealing times, were identified with ¹H NMR, FTIR, SEC, and MALDI‐TOF. Transurethanization was considerably faster for MDI‐based urethanes than for HDI‐based urethanes. Only traces of side products were formed during annealing of MDI‐based urethanes, whereas a significant amount of allophanates was formed from HDI‐based urethanes under the same conditions. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 621–629     

Liquid crystalline polyurethane. Polyurethanes containing bis-(p-oxymethylphenyl) terephthalate

Several polyurethanes based on bis-(p-oxymethylphenyl) terephthalate (BOPT) were synthesized and studied with respect to some of their thermal properties. BOPT exhibits a mesomorphic phase at 252–264°C. Polymerization was carried out by equimolar reaction with hexamethyl-ene diisocyanate (HDI), 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI) α,α'-diisocyanate-1,3-dimethylcyclohexane (H6 XDI), 4,4′-diphenylmeth-ane diisocyanate (MDI), 2,4-tolylene diisocyanate (TDI), and phenylene diisocyanate (PDI). It became clear that polyurethanes obtained from BOPT with HDI, H₁₂MDI, H₆XDI, and TDI have mesomorphic phases at 243–291, 214–250, 172–229, and 180–234°C, respectively, as determined by DSC and polarized microscopy, and that all polyurethanes are crystalline as evidenced by x-ray diffraction.     

Ring‐opening polymerization of substituted ε‐caprolactones with a chiral (salen) AlOiPr complex

The ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL), 4‐methyl‐ε‐caprolactone (4‐MeCL), and 6‐methyl‐ε‐caprolactone (6‐MeCL) with a single‐site chiral initiator, R,R′‐(salen) aluminum isopropoxide (R,R′‐[1]), was investigated. The kinetic data for the ROP of the three monomers at 90° in toluene corresponded to first‐order reactions in the monomer and propagation rate constants of k_ε‐CL > k_4‐MeCL ? k_6‐MeCL. A notable stereoselectivity with a preference for the R‐enantiomer was observed in the ROP of 6‐MeCL with R,R′‐[1], whereas for 4‐MeCL, no stereoselectivity was found. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 429–436, 2007.     

Polyurethane cationomers. I. Structure-property relationships

Polyether polyurethane cationomers are prepared using poly (tetramethylene oxide) of molecular weight 2000 as soft segments, N-methyl-diethanolamine as chain extender, glycolic acid as quaternization agent, methyl ethyl ketone as solvent, and three different diisocyanates. The three diisocyanates are 4,4′-diphenylenemethylene diisocyanate (MDI), hexamethylene diisocyanate (HDI), and toluene diisocyanate (TDI). Properties of the films cast from solutions of the three series of ionomers are studied by infrared spectroscopy, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry, wide angle x-ray diffraction, and tensile elongation testing. In the un-ionized and ionized systems, the hard segments exhibit disordered and ordered arrangements, respectively. Ionization disrupts the order and produces increased cohesion in the hard domains, which have opposing effects on the tensile elongation properties. In the MDI and TDI systems, cohesion is predominant, leading to an increased tensile strength and modulus and decreased elongation at break. But in the HDI system, the disruption of the order is predominant, leading to decreased tensile strength and only insignificant reduction in the elongation at break. In the TDI system, the tensile strength is rather low, which is attributed to the poor order in the hard domains resulting from the high content of the asymmetric 2,4-isomer of the urethane.     

Preparation and properties of imide‐containing elastic polymers from elastic polyureas and pyromellitic dianhydride

A new approach to obtain imide‐containing elastic polymers (IEPs) via elastic and high‐molecular‐weight polyureas, which were prepared from α‐(4‐aminobenzoyl)‐ω‐[(4‐aminobenzoyl)oxy]‐poly(oxytetramethylene) and the conventional diisocyanates such as tolylene‐2,4‐diisocyanate(2,4‐TDI), tolylene‐2,6‐diisocyanate(2,6‐TDI), and 4,4′‐diphenylmethanediisocyanate (MDI), was investigated. IEP solutions were prepared in high yield by the reaction of the polyureas with pyromellitic dianhydride in N‐methyl‐2‐pyrrolidone (NMP) at 165°C for 3.7–5.2 h. IEPs were obtained by the thermal treatment at 200°C for 4 h in vacuo after NMP was evaporated from the resulting IEP solutions. We assumed a mechanism of the reaction via N‐acylurea from the identification of imide linkage and amid acid group in IEP solutions. NMR and FTIR analyses confirmed that IEPs were segmented polymers composed of imide hard segment and poly(tetramethylene oxide) (PTMO) soft segment. The dynamic mechanical and thermal analyses indicated that the IEPs prepared from 2,6‐TDI and MDI showed a glass‐transition temperature (T_g ) at about −60°C, corresponding to T_g of PTMO segment, and suggested that microphase‐separation between the imide segment and the PTMO segment occured in them. TGA studies indicated the 10% weight‐loss temperatures (T₁₀) under air for IEPs were in the temperature range of 343–374°C. IEPs prepared from 2,6‐TDI and MDI showed excellent tensile properties and good solvent resistance. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 715–723, 2000     

Efficient synthesis of ionic triblock copolyesters and facile access to charge‐reversal hybrid micelles

Novel carboxyl‐ and amino‐functionalized copolyesters, based on poly(ε‐caprolactone)‐block‐poly(butylene fumarate)‐block‐poly(ε‐caprolactone), were efficiently synthesized via Michael‐type thiol‐ene click chemistry. The resulting amphiphilic copolyesters with controllable molecular weights and abundant positively or negatively charged groups could spontaneously form pH‐sensitive micelles in aqueous solutions, as confirmed by transmission electron microscopy, dynamic light scattering, fluorescence probing technique, and zeta potential analyses. Importantly, charge‐reversal hybrid micelles can be obtained by co‐assembly of carboxyl‐ and amino‐functionalized copolyesters. The surface charges of hybrid micelles reversed rapidly from negative to positive at isoelectric point via protonation of surface carboxyl and amino groups. Interestingly, the hybrid micelles showed apparent pH‐triggered Nile red‐release behavior in acidic condition resembling tumor intracellular environment, which is fairly desirable for drug delivery. Our work indicates that co‐assembly is a facile but efficient way to prepare charge‐reversal micelles, which have great potential to be used as intelligent drug delivery systems for cancer therapy. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1259–1267     

Synthesis of branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐ [linear‐poly(ε‐caprolactone)] by combination of glaser coupling reaction with ring‐opening polymerization

A novel amphiphilic branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐[linear‐poly(ε‐caprolactone)] [(l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL)] was synthesized by combination of glaser coupling reaction with ring‐opening polymerization (ROP) mechanism. The self‐assembling behaviors of (l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL) and their π‐shaped analogs of poly(ε‐caprolactone)/poly(ethylene oxide)]‐b‐poly(ethylene oxide)‐b‐[poly(ε‐caprolactone)/poly(ethylene oxide) with comparable molecular weight in water were preliminarily investigated. The results showed that the micelles formed from the former took a fiber look, however, that formed from the latter took a spherical look. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and crystallization of star‐shaped photocleavable poly(ε‐caprolactone)s

Here, we report on the synthesis and different crystallization behavior of linear‐ and star‐ PCL's containing a photocleavable linker (5‐hydroxy‐2‐nitro benzaldehyde), modulated by photochemical switching. Basis is the attachment of a photocleavable moiety close to the star‐core of a three‐arm star poly(caprolactone), so that the crystallization behavior can be controlled via a photochemical stimulus. The polymerization of ε‐caprolactone using a trivalent photocleavable initiator and stannous octanoate catalyst resulted in the synthesis of different molecular weights of star‐shaped photocleavable polymers. Various techniques like ¹H NMR and ESI‐TOF‐MS confirmed the successful synthesis of the star‐shaped polymers. Complete photocleavage is ensured via GPC, HPLC, and ESI‐TOF‐MS. DSC studies clearly indicated the enhancement in crystallinity after photocleavage of the star‐shaped poly(ε‐caprolactone)s. Hence, for the first time phototriggered crystallization behavior of PCL polymers is reported, where the confinement exerted by the star architecture is removed by photoirradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 642–649     

Thermoplastic elastomers based on poly(l‐Lysine)‐Poly(ε‐Caprolactone) multi‐block copolymers

Novel thermoplastic elastomers based on multi‐block copolymers of poly(l ‐lysine) (PLL), poly(N‐ε‐carbobenzyloxyl‐l ‐lysine) (PZLL), poly(ε‐caprolactone) (PCL), and poly(ethylene glycol) (PEG) were synthesized by combination of ring‐opening polymerization (ROP) and chain extension via l ‐lysine diisocyanate (LDI). SEC and ¹H NMR were used to characterize the multi‐block copolymers, with number‐average molecular weights between 38,900 and 73,400 g/mol. Multi‐block copolymers were proved to be good thermoplastic elastomers with Young's modulus between 5 and 60 MPa and tensile strain up to 1300%. The PLL‐containing multi‐block copolymers were electrospun into non‐woven mats that exhibited high surface hydrophilicity and wettability. The polypeptide–polyester materials were biocompatible, bio‐based and environment‐friendly for promising wide applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3012–3018     

Poly(thienyl‐phenylene)s with macromolecular side chains by oxidative polymerization of well‐defined macromonomers

Well‐defined polystyrene (PSt), poly(ε‐caprolactone) (PCL) or poly(2‐methyloxazoline) (POx) based polymers containing mid‐ or end‐chain 2,5‐ or 3,5‐dibromobenzene moieties were prepared by controlled polymerization methods, such as atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), or cationic ring opening polymerization (CROP). These polymers were subsequently modified by Suzuki type coupling reactions with 2‐thiophene boronic acid. The resulting polymers, containing a conjugated sequence with 2‐thienyl groups at the extremities, could be further used as macromonomers in chemical oxidative polymerization in the presence of anhydrous FeCl₃. Poly(thienyl‐phenylene)s having the respective PSt or PCL chains as lateral subtituents were obtained in this way. All the starting, intermediate, or final polymers were structurally analyzed by spectroscopic methods (¹H and ¹³C NMR, IR) and gel permeation chromatography (GPC) measurements. Thermal behavior of the macromonomers and final polymers was investigated by differential scanning calorimetry (DSC) analyses. Optical properties of the polymers were monitored by UV and fluorescence spectroscopy. The emission spectra of the polymers show a clear bathochromic shift of the λ_max emission in all the cases with respect to the monomers because of the extending of the conjugation length. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 848–865, 2007.     

Novel synthesis of biodegradable amphiphilic linear and star block copolymers based on poly(ε‐caprolactone) and poly(ethylene glycol)

Biodegradable, amphiphilic, diblock poly(ε‐caprolactone)‐block‐poly(ethylene glycol) (PCL‐b‐PEG), triblock poly(ε‐caprolactone)‐block‐poly(ethylene glycol)‐block‐poly(ε‐caprolactone) (PCL‐b‐PEG‐b‐PCL), and star shaped copolymers were synthesized by ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) methyl ether or poly(ethylene glycol) or star poly(ethylene glycol) and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature to yield monomodal polymers of controlled molecular weight. The chemical structure of the copolymers was investigated by ¹H and ¹³C NMR. The formation of block copolymers was confirmed by ¹³C NMR and DSC investigations. The effects of copolymer composition and molecular structure on the physical properties were investigated by GPC and DSC. For the same PCL chain length, the materials obtained in the case of linear copolymers are viscous whereas in the case of star copolymer solid materials are obtained with low T_g and T_m temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3975–3985, 2007     

Microwave‐assisted graft polymerization of ε‐caprolactone onto magnetite

The graft polymerization of ε‐caprolactone (ε‐CL) onto magnetite was carried out under microwave irradiation in the presence of tin(II) 2‐ethylhexanoate. The molar ratio of ε‐CL to tin(II) 2‐ethylhexanoate was 300, whereas the molar ratio of ε‐CL to magnetite was 5. The chemical structures of the obtained poly(ε‐caprolactone) coated magnetic nanoparticles were characterized by FTIR and XPS spectroscopy. These magnetic‐polymer hybrid nanostructures were further investigated by X‐ray diffraction and magnetization measurements. The morphology of the magnetic core‐shell nanostructures were determined by TEM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5397–5404, 2009     

Rheological properties and crystallization behavior of multi‐walled carbon nanotube/poly(ε‐caprolactone) composites

Multi‐walled carbon nanotube/poly(ε‐caprolactone) composites (PCLCNs) were prepared by melt compounding. The rheology, nonisothermal crystallization behavior, and thermal stability of PCLCNs were, respectively, investigated by the parallel‐plate rheometer, differential scanning calorimeter, and TGA. Cole–Cole plots were employed successfully to detect the rheological percolation of PCLCNs under small amplitude oscillatory shear. PCLCNs present a low percolation threshold of about 2–3 wt % in contrast to that of clay‐based nanocomposites. The percolated nanotube network is very sensitive to the steady shear deformation, and is also to the temperature, which makes the principle of time‐temperature superposition be invalid on those percolated PCLCNs. Small addition of nanotube cannot improve the thermal stability of PCL but can increase crystallization temperature remarkably due to the nucleating effect. As the nanotube is much enough to be percolated, however, the impeding effect becomes the dominant role on the crystallization, and the thermal stability increases to some extent. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3137–3147, 2007     

Amine-quinone polyurethanes. I. Preparation of polyurethane block copolymers containing 2,5–bis(N-2-hydroxyethyl-N-methylamino)-1,4–benzoquinone diol monomer

The amine-quinone monomer, 2,5–bis(N-2-hydroxyethyl-N-methylamino)-1,4-benzoqui-none (AQM-1), was prepared by the multiple-step condensation of 2-(N-methylam-ino)ethanol with benzoquinone in the presence of oxygen. This crystalline monomer was used to prepare a series of amine-quinone polyurethanes by condensation polymerization, either in the melt or in solution (THF or DMF), with a diisocyanate (MDI, TDI, or IPDI) and an oligomeric diol [poly(caprolactone) or poly(1,2-butylene glycol)]. The amine-quinone functional group was stable under the polymerization conditions, and was incorporated into the main chain, giving red-brown polyurethanes that had molecular weights in the range of 11,000–90,000 and were soluble in THF, MEK, DMF, and DMSO. The thermal properties were consistent with a two-phase morphology with an amorphous soft segment, containing the oligomeric diol, and a microcrystalline hard segment, containing AQM-1. The polymers having a low hard segment content (<50%) were rubbery (soft segment T_g <?25°C); polymers having a high hard segment content (>50%) were thermoplastic (hard segment T_g>150°C). © 1995 John Wiley & Sons, Inc.     

Oxazoline‐terminated macromonomers by the alkylation of 2‐methyl‐2‐oxazoline

Well‐defined macromonomers of poly(ethylene oxide) and poly(tert‐butyl methacrylate) were obtained by anionic polymerization induced directly by the carbanion issued from 2‐methyl‐2‐oxazoline. When ethylene oxide was added to this carbanion with lithium as the counterion, a new compound able to initiate the polymerization of ε‐caprolactone in an anionically coordinated way was synthesized, and this led to well‐defined poly(ε‐caprolactone) macromonomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2440–2447, 2005