Rendering polyureas melt processible

Because of the presence of extensive H‐bonding in the hard segments, polyureas are processed by solution techniques (e.g., dry spinning) by the use of relatively costly and environmentally unfriendly solvents. Thus, the objective of this research was to render polyureas melt processible, (i.e., to reduce their flow temperature, T_flow) without compromising their excellent mechanical properties. We hypothesized and herein demonstrate that by using conventional chain extenders (CEs) in combination with small amounts of H‐bond acceptor chain extenders (HACEs), the T_flow of polyureas can be significantly reduced from ～230 to ～180 °C, and thus melt processible products with excellent mechanical properties can be obtained. We document the synthesis of conventional polytetramethylene oxide‐based and novel polyisobutylene (PIB)‐based polyureas with T_flows ～ 180 °C and excellent mechanicals by the addition of few percents of commercially available HACEs. Products were characterized by various techniques, including Instron (tensile strengths, elongations), durometer (Shore A Hardness), dynamic mechanical thermal analysis (T_flow), and thermal gravimetric analysis (TGA) (thermal weight loss). According to TGA, a polyurea with T_flow of ～180 °C did not degrade up to ～234 °C in air. A micromorphology for melt processible polyureas is proposed that emphasizes flexibilized hard segments in the presence of HACEs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polyisobutylene‐based polyurethanes. II. Polyureas containing mixed PIB/PTMO soft segments

The design, synthesis, characterization, and structure–property behavior of polyureas containing novel soft segments of mixed polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) chains and conventional hard segments is presented. Modest amounts (12%) of PTMO in the soft PIB phase significantly increase both the tensile strength and elongation of the polyureas. These polyureas exhibit not only oxidative/hydrolytic stabilities far superior to Bionate® and Elast‐Eon® considered the most oxidatively stable polyurethanes on the market but also display mechanical properties (29 MPa tensile strength and 200% elongation) approaching those of conventional thermoplastic polyurethanes. The surfaces of these polyureas are covered/protected by PIB segments, which will lead to excellent biocompatibility. Our results demonstrate that the PTMO segments facilitate stress transfer from the continuous mixed soft phase to the dispersed hard phase, which strengthens and flexibilizes PIB‐based polyureas and thus significantly improves elastomeric properties without compromising oxidative and hydrolytic stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2787–2797, 2009     

Synthesis and Characterization of Thermoplastic Polyurethaneureas based on Polyisobutylene and Poly(tetramethylene oxide) Segments

New thermoplastic polyurethaneureas (TPUU) based on polyisobutylene (PIB) and poly(tetramethylene oxide) (PTMO) segments have been synthesized possessing tensile properties comparable to conventional PTMO based TPUs. PIB based TPUU containing 35 weight (wt)% hard segment was synthesized by chain extension of H₂N-Allyl-PIB-Allyl-NH₂ with 4,4′ -methylene bis(phenylisocyanate) (MDI) and 1,4-butanediol (BDO) in toluene. The ultimate tensile strength (UTS) = 12 MPa and ultimate elongation = 70% were inferior to PTMO based polyurethane (UTS = 35 MPa, elongation at break = 600%). H₂N-Allyl-PIB-Allyl-NH₂ and HO-PTMO-OH in different proportions were chain extended in presence of MDI and BDO to obtain TPUUs containing 35 wt% hard segment. The polymers exhibited M _ns = 84000–138000 with polydispersity indices (PDIs) = 1.7–3.7. The UTS = 23–32 MPa and elongation at break = 250–675% was comparable to that of PTMO based polyurethane and significantly higher than the PIB based TPUU with the same Shore hardness. The Young's modulus of the polymers was strongly dependent and directly proportional to the PIB wt% in the SS of the TPUUs.     

Polyisobutylene‐based polyurethanes. V. Oxidative‐hydrolytic stability and biocompatibility

The oxidative/hydrolytic stability of polyurethanes (PUs) containing exclusively polyisobutylene (PIB), or mixed PIB/polytetramethylene oxide (PTMO), or mixed PIB/polyhexamethylene carbonate (PC) soft segments was investigated. The tensile strengths and elongations of various PUs were determined before and after agitating in 35% HNO₃ or 20% H₂O₂/0.1 M CoCl₂ solutions and retentions were quantified. The presence of PIB imparts significant oxidative/hydrolytic resistance. The tensile strength and elongation of PUs containing 70% PIB, or those of mixed PIB/PC soft segments with 50% PIB, remained essentially unchanged upon exposure to HNO₃; in contrast, PUs containing mixed PIB/PTMO soft segments with 50% PIB underwent significant degradation. The tensile strength of PUs with mixed PIB/PC (60/10%) soft segment increased after exposure to HNO₃, most likely because of oxidative crosslinking of PC segments. PIB/PTMO‐ and PIB/PC‐based PUs and commercially available PUs (Elast‐Eon® and Carbothane®) were exposed to H₂O₂/CoCl₂ solutions for up to 14 weeks. Although the experimental PIB/PC‐based PUs exhibited negligible change in mechanical properties and no surface damage, Elast‐Eon® and Carbothane® showed significant surface damage. PIB‐based polyureas and Bionate® were implanted in rats for 4 weeks in vivo, and their biocompatibility was investigated. The biocompatibility of PIB‐based materials was superior to Bionate®. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2194–2203, 2010     

Synthesis and characterization of N‐substituted hyperbranched polyureas

N,N′‐disubstituted hyperbranched polyureas with methyl, benzyl, and allyl substitutents were synthesized starting from AB₂ monomers based on 3,5‐diamino benzoic acid. Carbonyl azide approach, which generates isocyanate group in situ on thermal decomposition, was used for the protection of isocyanate functional groups. The N‐substituted hyperbranched polymers can be considered as the new class of internally functionalized hyperbranched polyureas wherein the substituent can function either as receptor or as a chemical entity for selective transformations as a tool to tailor the properties. The chain‐ends were also modified by attaching long chain aliphatic groups to fully realize the interior functionalization. This approach opens up a possible synthetic route wherein different functional substituents can be used to generate a library of internally functionalized hyperbranched polymers. All the hyperbranched polyureas were characterized by FTIR, ¹H‐NMR, DSC, TGA, and size exclusion chromatography. Degree of branching in these N,N′‐disubstituted hyperbranched polyureas, as calculated by ¹H‐NMR spectroscopy using model compounds, was found to be lower than the unsubstituted hyperbranched polyurea and is attributed to the lower reactivity of N‐substituted amines compared to that of unsubstituted amines. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5134–5145, 2004     

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     

Design,syntheses, and characterization of new thermoplastic polyureas based on 3,4‐ethylenedioxythiophene

New thermoplastic polyureas labeled PUn (n = 2, 3, 4, 6, 7, 9, or 10), based on 3,4‐ethylenedioxythiophene (EDOT) with flexible aliphatic spacers, were synthesized and characterized for the first time. EDOT was chosen as a replacement for the aromatic phenyl group in conventional thermoplastics based on urea linkages to improve solubility without compromising the thermal properties. As synthesized, all the samples exhibited a semicrystalline nature. The glass‐transition and melting temperatures showed a strong dependence on the spacer length. A comparison of the thermal properties of these polyureas with the corresponding phenyl analogues indicated that EDOT was a viable heteroatomic analogue of the phenyl group to be inserted into the main‐chain polyureas without hampering their thermal stability. The polyureas with spacer lengths greater than hexamethylene formed transparent gels in N‐methylpyrrolidone, 1,1,2,2‐tetrachloroethane, and dimethyl sulfoxide. The molecular packing of the polyureas was assigned with wide‐angle X‐ray diffraction studies. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5823–5830, 2005     

Amphiphilic conetworks. IV. Poly(methacrylic acid)‐l‐polyisobutylene and poly(acrylic acid)‐l‐polyisobutylene based hydrogels prepared by two‐step polymer procedure. New pH responsive conetworks

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(methacrylic acid) (PMAA) or poly(acrylic acid) (PAA) and hydrophobic polyisobutylene (PIB) chains. These conetworks were prepared by a two‐step polymer synthesis. In the first step, a cationic copolymer of isobutylene (IB) and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB–IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2‐hydroxyethyl methacrylate (HEMA). In the second step, the resulting MA‐multifunctional PIB‐based crosslinker, PIB(MA)_n, with an average functionality of approximately four methacrylic groups per chain, was copolymerized with methacrylic acid (MAA) or acrylic acid (AA) by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 31–79 mol % of MAA or 26–36 mol % of AA. The synthesized conetworks were characterized with solid‐state ¹³C‐NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proven by swelling in both aqueous media with low and high pH and n‐heptane. The effect of varying pH on the swelling behavior of the synthesized conetworks is presented. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1284–1291, 2009     

Polyisobutylene‐based polyurethanes X: PU nanocomposites with s‐containing soft segments

Sulfur‐containing polyisobutylene (PIB)‐based polyurethane nanocomposite (PIB_s‐PU/NC) was synthesized using HO? CH₂CH₂? S? PIB? S? CH₂CH₂? OH for the soft segment, conventional hard segments of MDI and BDO, and organically modified montmorillonite (OmMMT) nanolayers. The properties of PIB_s‐PU/NC containing 72.5% PIB and 0.5% OmMMT were studied and contrasted with unmodified PIB_s‐PU. PIB_s‐PU/NC produces colorless optically clear films exhibiting enhanced tensile strength, elongation, oxidative–hydrolytic stability, and creep resistance relative to that of PIB_s‐PU. FTIR spectroscopy indicates H bonded S atoms between soft and hard segments, and OmMMT nanolayers. DSC and XRD suggest randomly dispersed low‐periodicity crystals and urea groups between galleries. We propose that minute amounts of OmMMT nanolayers become covalently attached to polyurethane chains and beneficially affect properties by acting as co‐chain extender/reinforcing filler. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2760–2765     

Syntheses,characterization, and properties of multiblock copolymers consisting of polyisobutylene and poly(L‐lactide) segments

The syntheses of {‐poly(L ‐lactide) (PLLA)‐b‐polyisobutylene (PIB)‐}_n multiblock copolymers were accomplished for the first time by chain extension of PLLA‐b‐PIB‐b‐PLLA triblock copolymers. Well‐defined PLLA‐b‐PIB‐b‐PLLA triblock copolymers with predictable M_ns, low PDIs (1.10–1.18) and excellent blocking efficiencies were prepared by anionic ring‐opening polymerizations of L ‐lactide initiated with hydroxyallyl telechelic PIB (HO‐Allyl‐PIB‐Allyl‐OH) in toluene at 110 °C. The triblock copolymers were successfully chain extended with 4,4′‐methylenebis(phenylisocyanate) (MDI) to obtain the multiblock copolymers with good gravimetric yields of ～86 to 96%. The chain‐extended polymers were soluble in a range of common organic solvents. The block copolymers showed two glass transition temperatures in differential scanning calorimetric analysis for the PIB and PLLA blocks indicating microphase separation, which was supported by atomic force microscopy images. The as‐synthesized compression molded multiblock copolymers exhibited tensile strengths in the range of 8–24 MPa with elongations at break in the range of 2.5–400%. The static and dynamic mechanical properties showed a strong dependence on the relative PLLA content in the copolymer. The dynamic mechanical analysis also indicated microphase separation at higher PLLA compositions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3490–3505, 2009     

Microphase separation in RIM polyureas as studied by solid-state NMR

The microphase separation (MPS) in polyureas based on methylene diphenyl diisocyanate (MDI) hard segment, diethyltoluenediamine chain extender, and amino-terminated polypropylene glycol soft segment prepared by reaction injection molding (RIM) was studied by advanced solid-state NMR spectroscopy. Incomplete microphase separation leads to the presence of mobilized hard segments dispersed in the soft segment domains as well as immobilized soft segments residing in the hard domains. This is detected by ¹H-NMR spectra recorded under spinning at the magic angle (MAS) as well as two-dimensional wide-line separation (WISE) NMR spectra. The sizes of the various domains as well as the interfaces between them are quantified by spin diffusion measurements. In this way the impact of annealing, method of polymerization, and hard segment content on MPS is studied. Whereas annealing at temperatures up to 170°C results in improving the MPS, major changes are observed after annealing at higher temperatures (190°C), where the system changes from “soft-in-hard” to “hard-in-soft” behavior. The MPS decreases with increasing hard segment content. The highest MPS is observed for solution polymerized samples. The various NMR experiments clearly reveal the nonequilibrium nature of RIM systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 693–703, 1998     

Minute amounts of organically modified montmorillonite improve the properties of polyisobutylene‐based polyurethanes

We discovered that polyisobutylene (PIB)‐based polyurethanes (PIB‐PUs) containing minute amounts (0.5%) of chemically bound organically modified montmorillonite (OmMMT) surprisingly produce films exhibiting improved properties. The OmMMT was prepared by reacting sodium montmorillonite (Na⁺MMT^?) with quaternary ammonium salts of a tertiary amine carrying a ? NH₂ functionality. The positively charged quaternary amine group becomes electrostatically attached to negatively charged MMT layers and defoliates it, whereas the free ? NH₂ group reacts with diisocyanates and acts as an additional chain extender. Thus, when OmMMT is added to a mixture of ingredients assembled for the synthesis of PIB‐PUs, this modified clay becomes an integral part of the PU. Specifically, we found that the integration of 0.5% OmMMT to PIB‐based PUs produces films with significantly enhanced tensile strength, elongation, toughness, creep, and stress relaxation relative to that of PIB‐PUs. The findings were discussed and explained in terms of a proposed morphology for the nanocomposite. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4076–4087     

Amphiphilic conetworks. III. Poly(2,3‐dihydroxypropyl methacrylate)–polyisobutylene and poly(ethylene glycol) methacrylate–polyisobutylene based hydrogels prepared by two‐step polymer procedure

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(2,3‐dihydroxypropyl methacrylate) or poly(ethylene glycol) methacrylate (PEGMA) and hydrophobic polyisobutylene chains. This conetworks were prepared by a two‐step polymer synthesis. In the first step, a cationic copolymer of isobutylene and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB‐IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2‐hydroxyethyl methacrylate (HEMA). In the second step, the resulting MA‐multifunctional PIB‐based crosslinker, PIB(MA)_n, with an average functionality of approximately four per chain, was copolymerized with 2,3‐dihydroxypropyl methacrylate or poly(ethylene glycol) methacrylate by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 11–60 mol % of DHPMA or 10–12 mol % of PEGMA. The synthesized conetworks were characterized with solid‐state ¹³C‐NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proved by swelling in both water and n‐heptane. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4074–4081, 2007     

Polyisobutylene‐based polyurethanes. VIII. Polyurethanes with ‐O‐S‐PIB‐S‐O‐ soft segments

We describe the synthesis, characterization, and select properties of a novel polyurethane (PU) prepared using a new polyisobutylene diol, HO‐CH₂CH₂‐S‐PIB‐S‐CH₂CH₂‐OH, soft segment and conventional hard segments. The diol is synthesized by terminal functionalization of ally‐telechelic PIB followed by low‐cost thiol‐ene click chemistry. Properties of ‐S‐ containing PU (PIB_S‐PU) containing 72.5% PIB were investigated and compared to similar PUs made with HO‐PIB‐OH (PIB_O‐PU). Hydrolytic resistance was studied by contact with phosphate‐buffered saline, oxidative resistance by immersing in concentrated HNO₃, and metal ion oxidation resistance by exposure to CoCl₂/H₂O₂. Hydrolytic and oxidative resistances of PIB_S‐PU and PIB_O‐PU are similar and superior to a commercial PDMS‐based PU, Elast‐Eon? E2A. According to ¹H NMR spectroscopy the ‐S‐ in PIB_S‐PUs remained unchanged upon treatment with HNO₃, however, oxidized mainly to ‐SO₂‐ by CoCl₂/H₂O_2. Static mechanical properties of PIB_S‐PU and PIB_O‐PU are similar, except creep resistance of PIB_S‐PU is surprisingly superior. The thermal stability of PIB_S‐PUs is ～15 °C higher than that of PIB_O‐PU. FTIR spectroscopy indicates H bonded S atoms (N‐H…S) between soft and hard segments, which noticeably affect properties. DSC and XRD studies suggest random low‐periodicity crystals dispersed within a soft matrix. Energy dispersive X‐ray spectroscopy–scanning electron microscopy indicates homogeneous distribution of S atoms on PIB_S‐PU surfaces. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1119–1131     

One‐pot synthesis of isocyanate and methacrylate multifunctionalized polyisobutylene and polyisobutylene‐based amphiphilic networks

Amphiphilic polymer networks consisting of hydrophilic poly(2‐hydroxyethyl methacrylate) (PHEMA) and hydrophobic polyisobutylene (PIB) chains were synthesized from a cationic copolymer of isobutylene (IB) and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) prepared at ?50 °C in dichloromethane in conjunction with SnCl₄. The isocyanate groups of this random copolymer, PIB(NCO)_n, were subsequently transformed in situ to methacrylate (MA) groups in the dibutyltin dilaurate‐catalyzed reaction with 2‐hydroxyethyl methacrylate (HEMA) at 30 °C. The resulting PIB(MA)_n with number–average molecular weight 8200 and average functionality F_n ～ 4 per chain was in situ copolymerized radically with HEMA at 70 °C, giving rise to the amphiphilic networks containing 41 and 67 mol % HEMA. PHEMA–PIB network containing 43 mol % HEMA was also prepared by radical copolymerization of PIB(MA)_n precursor with HEMA using sequential synthesis. An amphiphilic nature of the resulting networks was proved by swelling in both water and n‐heptane. PIB(NCO)_n and PIB(MA)_n were characterized by FTIR spectroscopy, SEC and the latter also by ¹H NMR spectroscopy. Solid state ¹³C NMR spectroscopy was used for characterization of the resulting PHEMA–PIB networks. Whereas single glass‐transition temperature, T_g = ?67.4 °C, was observed for the rubbery crosslinked PIB prepared by reaction of PIB(NCO)_n with water, the PHEMA–PIB networks containing 67 and 41 mol % HEMA showed two T_g's: ?70.4 and 102.7 °C, and ?63 and 107.2 °C, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2891–2900, 2006     

Rubbery wound closure adhesives. I. design,synthesis, characterization,and testing of polyisobutylene‐based cyanoacrylate homo‐ and co‐networks

Novel rubbery wound closures containing various proportions and molecular weights of polyisobutylene (PIB) and poly(2‐octyl cyanoacrylate) [P(OctCA)] for potential clinical use were designed, synthesized, characterized, and tested. Homo‐networks were prepared by crosslinking 3‐arm star‐shaped PIBs fitted with terminal cyanoacrylate groups, [Ø(PIB‐CA)₃], and co‐networks by copolymerizing Ø(PIB‐CA)₃ with OctCA using N‐dimethyl‐p‐toluidine (DMT). Neat Ø(PIB‐CA)₃, and Ø(PIB‐CA)₃/OctCA blends, upon contact with initiator, polymerize within seconds to optically transparent strong rubbery co‐networks, Ø(PIB‐CA)₃‐co‐P(OctCA). Homo‐ and co‐network formation was demonstrated by sol/gel studies, and structures and properties were characterized by a battery of techniques. The T_g of P(OctCA) is 58 °C by DSC, and 75 °C by DMTA. Co‐networks comprising 25% Ø(PIB‐CA)₃ (M_n = 2400 g/mol) and 75% P(OctCA) are stronger and more extensible than skin. Short and long term creep studies show co‐networks exhibit high dimensional stability and <6% creep strain at high loading. When deposited on porcine skin co‐networks yield hermetically‐adhering clear rubbery coatings. Strips of porcine skin coated with co‐networks could be stretched and twisted without compromising membrane integrity. The co‐network is nontoxic to L‐929 mouse fibroblasts. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1640–1651     

Polyisobutylene‐based polyurethanes. IX. synthesis,characterization, and properties of polyisobutylene‐based poly(urethane‐ureas)

Polyisobutylene (PIB)‐based polyurethanes (PUs) exhibit unparalleled hydrolytic‐oxidative‐biologic stability and are melt processible, however, their mechanical (strength) properties are modest mainly due to insufficient H bonds. We posited and demonstrate that the ultimate properties of PIB‐PUs are enhanced, while their melt processibility is maintained, by the judicious introduction of urea linkages, i.e., strong bifurcated H bonds, in the chain. The incorporation of bifurcated H bonds in PIB‐PUs was achieved by using the conventional butane diol chain extender (CE) in combination with controlled amounts of amino alcohol as co‐chain extender (co‐CE). Polyurethanes containing both urethane and urea linkages are polyurethane‐ureas (PUU). Specifically, PIB‐PUUs prepared with PIB‐diol/MDI together with 80/20 mole % butane diol/amino butanol exhibited ～30 MPa tensile strength, ～550% elongation, ～80 Shore A hardness, and ～137 °C flow temperature. Other amino alcohols, i.e., amino ethanol, ‐propanol, and ‐hexanol, were less effective co‐CEs. ¹H‐NMR and FT‐IR spectroscopies indicate the presence of bifurcated H bonds in PIB‐PUUs prepared with CE/co‐CE combinations. Characterization by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, and creep experiments also suggest bifurcated H bonds in PIB‐PUU. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2361–2369     

Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [Ph? C(CH₃)(CH₂OH)–PIB–CH₂? C(CH₃)₂Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from ?75 to ?50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ～ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and ¹H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and ¹H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002     

Polyisobutylene containing organic/inorganic hybrid block copolymers and their crystalline behavior

Block copolymer comprising of polyisobutylene (PIB) soft segment and poly(3‐(3,5,7,9,11,13,15‐heptaisobutyl‐pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]‐octasiloxane‐1‐yl)propyl methacrylate) (PMAPOSS) hard segment was synthesized by combination of living carbocationic and reversible addition‐fragmentation chain transfer (RAFT) polymerizations. Block copolymers were characterized by ¹H and ²⁹Si NMR spectroscopy, FT‐IR study, energy dispersive X‐ray spectroscopy (EDX), and gel permeation chromatography (GPC). The EDX, combined with scanning electron microscopy (SEM) was employed for determination of elemental composition. Thermal transition and degradation behaviors were confirmed by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), respectively. Although both the PIB and MAPOSS homopolymers are amorphous in nature, in their block copolymers the PMAPOSS domain showed crystalline behavior, as confirmed from wide‐angle X‐ray scattering (WAXS) technique, DSC studies and polarized optical microscopy (POM). Interestingly, crystalline melting temperatures (T_m) can be tuned by changing the PIB to PMAPOSS block length ratios. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1125–1133     

Polyisobutylene‐based polyurethanes: VII. structure/property investigations for medical applications

The outstanding hydrolytic and oxidative stabilities of polyisobutylene‐based polyurethanes (PIB‐based PUs) were reported earlier. Herein, we summarize recent investigations aimed at further enhancing hydrolytic‐oxidative stabilities (in terms of resistance to aqueous buffer, nitric acid and CoCl₂/H₂O₂) together with excellent mechanical properties. The purity and dryness of ingredients together with precise NCO/OH stoichiometry (～1.05) are essential to obtain PIB‐based PUs with improved properties. Static and dynamic mechanical properties were optimized by analyzing stress–strain traces, thermal (TGA, DSC) responses, self‐organization (XRD) profiles, and rheological (DMA, creep) information. According to microstructure and surface analyses (AFM, contact angle) annealing increases the segregation of individual segments and increases surface hydrophobicity, which in turn enhances the shielding of hydrolytically oxidatively vulnerable carbamate bonds by inert PIB barriers, and thus significantly improves hydrolytic‐oxidative stability. Annealing does not much affect bulk properties, such as static and dynamic mechanical and thermal properties; however, it increases damping over a wide temperature range. Annealed PIB‐based PU containing 72.5% PIB exhibits outstanding hydrolytic‐oxidative stability together with ～26 MPa tensile strength, ～500% elongation, and ～77 Microshore hardness. PIB‐based PUs are significantly more resistant to hydrolytic and oxidative degradation than ElastEon? E2A, a commercially available PDMS‐based PU, widely used for medical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 532–543