Synthesis and characterization of calcium containing poly(urethane-ether)s

Calcium containing poly(urethane-ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate or toluylene 2,4-diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and polyethylene glycol (PEG₂₀₀ or PEG₄₀₀). A series of calcium containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:PEG₂₀₀ or PEG₄₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4 and 1:3:4 to study the effect of calcium content on the properties of the copolymer. The structure of the polymers were confirmed by IR, ¹H-NMR, ¹³C-NMR, and solid state ¹³C-CP-MAS NMR. The polymers were soluble in dimethyl sulfoxide and dimethyl formamide. The initial decomposition temperature of the polymers decreases with increase in calcium content. The T_g value of PUEs increases with increase in calcium content and decreases with increase in soft segment content and length. A single T_g value is observed for the calcium containing PUEs based on PEG₂₀₀ shows the presence of homogeneous phase. However, two T_g values for the PUEs based on PEG₄₀₀ for various composition of Ca(HBP)₂, PEG₄₀₀ and diisocyanate (HMDI or TDI) shows the presence of heterogeneous phase. The viscosity of the calcium containing PUEs increases with increase in the soft segment content as well as its length and decreases with increase in calcium content. X-ray diffraction patterns of the polymers show that the HMDI based polymers are partially crystalline and TDI based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium containing PUEs based on HMDI shows that at any given temperature modulus (g^′ and g^″) increases with increase in the ionic content in the polymers.     

Synthesis of zinc-containing poly(urethane-ether)s based on zinc salt of mono(hydroxypentyl)phthalate

Zinc salt of mono(hydroxypentyl)phthalate, Zn(HPP)₂, was synthesized by reacting 1,5-pentanediol, phthalic anhydride and zinc acetate. Zinc-containing poly(urethane-ether)s (PUEs) were synthesized by reacting hexamethylene diisocyanate (HMDI) or toluene 2,4-diisocyanate (TDI) with a mixture of Zn(HPP)₂ and poly(ethylene glycol) (PEG₃₀₀ or PEG₄₀₀) in dimethylsulfoxide (DMSO) at 95 °C under nitrogen atmosphere using di-n-butyltin dilaurate as a catalyst. Blank PUEs without Zn(HPP)₂ were also prepared by reacting PEG₃₀₀ or PEG₄₀₀ with HMDI or TDI under similar conditions. The structure of the polymers was confirmed by FT-IR, ¹H NMR, ¹³C NMR, and solid-state ¹³C-CP-MAS NMR spectra. The zinc-containing polymers were soluble in only highly polar solvents. The inherent viscosity of the zinc-containing PUEs was found to be very low. X-ray diffraction studies revealed that HMDI-based (PUEs) were partially crystalline while TDI based (PUEs) were amorphous. The T_g values of the zinc-containing PUEs were found to be low and range from 5.3 to 7.5 °C. The thermogravimetric analysis revealed the influence of zinc on the initial decomposition and the overall thermal stability of the polymers.     

Calcium‐containing poly(urethane‐urea)s: Synthesis,spectral, and thermal studies

A calcium salt of mono(hydroxypentyl)phthalate [Ca(HPP)₂] was synthesized by the reaction of 1,5‐pentanediol, phthalic anhydride, and calcium acetate. Four different bisureas such as hexamethylene bis(ω,N‐hydroxyethylurea), tolylene 2,4‐bis(ω,N‐hydroxyethylurea), hexamethylene bis(ω,N‐hydroxypropylurea), and tolylene 2,4‐bis(ω,N‐hydroxypropylurea) were prepared by reacting ethanolamine or propanolamine with hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI). Calcium‐containing poly(urethane‐urea)s (PUUs) were synthesized by reacting HMDI or TDI with 1:1 mixtures of Ca(HPP)₂ and each of the bisureas with di‐n‐butyltin dilaurate as a catalyst. The PUUs were well characterized by Fourier transform infrared spectroscopy, ¹H and ¹³C NMR, solid‐state ¹³C–cross‐polarization/magic‐angle spinning NMR, viscosity, solubility, elemental analysis, and X‐ray diffraction studies. Thermal properties of the polymers were also examined with thermogravimetric analyses and differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1809–1819, 2004     

Effect of the composition ratio of copolymerized poly(carbonate) glycol on the microphase‐separated structures and mechanical properties of polyurethane elastomers

Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C₆) and tetramethylene (C₄) units between carbonate groups in various composition ratios (C₄/C₆ = 0/100, 50/50, 70/30, and 90/10), and the number‐average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass‐transition temperature of the soft segment in the PUEs and the glass‐transition temperature of the original glycol polymer decreased and the melting point of the hard‐segment domain increased with an increasing C₄ composition ratio. The microphase separation of the poly(carbonate) glycol‐based PUEs likely became stronger with an increasing C₄ composition ratio. Young's modulus of these PUEs increased with an increasing C₄ composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C₄ composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase‐separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase‐separated structure and mechanical properties of the PUEs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4448–4458, 2004     

Effect of the diisocyanate on the structure and properties of polyurethane acrylate prepolymers

In this study, we investigated the role of diisocyanate on the properties of polyurethane acrylate (PUA) prepolymers based on polypropylene oxide (M̄_n = 2000 g · mol⁻¹). The diisocyanates studied were isophorone diisocyanate, 4‐4′dicyclohexylmethane diisocyanate, and toluene diisocyanate (pure 2,4‐TDI, pure 2,6‐TDI, and a TDI mixture, TDI_tech). The molecular structure of the diisocyanate had a major role on the course of the polycondensation and, more precisely, on the sequence length distribution of the final prepolymer. Moreover, the structural organization of the prepolymer also strongly depended on the nature of the diisocyanate. Two types of behaviors were particularly emphasized. On the one hand, the PUA synthesized from 2,4‐TDI displayed an enhanced intermixing between soft polyether segments and hard urethane groups, as revealed by the analysis of hydrogen bonding in Fourier transform infrared. Consecutively, the glass transition shifted to higher temperatures for these polymers. On the other hand, strong hard–hard inter‐urethane associations were observed in 2,6‐TDI‐based prepolymers; these led to microphase segregation between polyether chains and urethane groups, as revealed by optical microscopy. This inhomogeneous structure was thought to be responsible for the unusual rheological behavior of these PUA prepolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2750–2768, 2000     

Cyclotrimerization of diisocyanates toward high‐performance networked polymers with rigid isocyanurate structure: Combination of aromatic and aliphatic diisocyanates for tunable flexibility

A series of networked polymers bearing isocyanurate moiety was synthesized by cyclotrimerization of diisocyanates, with employing methylenediphenyl 4,4′‐diisocyanate and 1,6‐hexamethylenediisocyanate (HMDI) in several feed ratios. In spite of the large difference in intrinsic reactivity between these two diisocyanates, their coannulation proceeded efficiently by using sodium p‐toluenesulfinate (pTolSO₂Na) and 1,3‐dimethyl‐2‐imidazolidinone as a catalyst and a solvent, respectively. The resulting networked polymers were transparent and exhibited excellent thermal stability. In addition, HMDI‐rich feed ratios allowed for the formation of networked polymers with increased flexibility. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2631–2637     

Synthesis and properties of segmented main‐chain liquid‐crystalline polyurethanes with a high aspect ratio mesogenic diol as a chain extender

Main‐chain liquid‐crystalline polyurethanes were synthesized based on a high aspect ratio mesogenic diol (4‐{[4‐(6‐hydroxyhexyloxy)‐phenylimino]‐methyl}‐benzoic acid 4‐{[4‐(6‐hydroxyhexyloxy)‐phenylimino]‐methyl}‐phenyl ester) as a chain extender; polycaprolactone (PCL) diol soft segments of different number‐average molecular weights (530, 1250, or 2000); and different diisocyanates, including 1,4‐hexamethylene diisocyanate (HMDI), 4,4′‐methylene bis(cyclohexyl isocyanate) (H₁₂MDI), and 4,4′‐methylene bis(phenyl isocyanate) (MDI). The structure of the polymers was confirmed with Fourier transform infrared spectroscopy, and differential scanning calorimetry and polarizing microscopy measurements were carried out to examine the liquid‐crystalline and thermal properties of the polyurethanes, respectively. The mesogenic diol was partially replaced with 20–50 mol % PCL. A 20 mol % mesogen content was sufficient to impart a liquid crystalline property to all the polymers. The partial replacement of the mesogenic diol with PCL of various molecular weights, as well as the various diisocyanates, influenced the phase transitions and the occurrence of mesophase textures. Characteristic liquid‐crystalline textures were observed when a sufficient content of the mesogenic diol was present. Depending on the flexible spacer length and the mesogenic content, grained and threadlike textures were obtained for the HMDI and H₁₂MDI series polymers, whereas the polyurethanes prepared from MDI showed only grained textures for all the compositions. The polymers formed brittle films and could not be subjected to tensile tests. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1527–1538, 2002     

Sugar‐based hydrophilic polyurethanes and polyureas

Novel linear homogeneous polyurethanes and polyureas with enhanced hydrophilic character have been successfully prepared from sugar‐based monomers having their hydroxyl groups free or partially protected. By the reaction of primary hydroxyl groups of xylitol with dimethyl hexamethylene dicarbamate (HMDC) or di‐tert‐butyl‐4,4′‐diphenyl methyl dicarbamate (MDC), two new linear semicrystalline polyurethanes [PU(X‐HMDC) and PU(X‐MDC)] have been prepared. Likewise, by the reaction of xylitol with the analogous diisocyanates hexamethylene diisocyanate (HMDI) or 4,4′‐methylenebis(phenyl isocyanate) (MDI), similar polyurethanes [PU(X‐HMDI) and PU(X‐MDI)] were obtained. However, these latter polyurethanes present some degree of crosslinking because of the higher reactivity of the diisocyanate comonomers. Linear hydrophilic polyureas having free hydroxyl groups joined to the main chain have also been prepared by the reaction of the same diisocyanates (HMDI and MDI) with 1,6‐diamino‐1,6‐dideoxy‐D ‐mannitol and 1,6‐diamino‐1,6‐dideoxy‐3:4‐O‐isopropylidene‐D ‐mannitol. As far as we are aware, this kind of polyhydroxylated polyurea has not been previously described in the literature. The new polymers were characterized by standard methods (elemental analyses, gel permeation chromatography, IR, and NMR). The polyurethanes were hydrolytically degradable under physiological conditions, in contrast with less‐hydrophilic linear polyurethanes previously described. The thermal properties of the novel polymers were investigated by thermogravimetric analysis and differential scanning calorimetry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of side groups of polymer glycol on microphase‐separated structure and mechanical properties of polyurethane elastomers

The effect of side methyl and dimethyl groups of the soft segment component on the microphase‐separated structure and mechanical properties of polyurethane elastomers (PUEs) was investigated. Poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG‐X) and methyl side groups (PTG‐L) were used as a polymer glycol, which forms a soft segment in the PUEs. The PUEs were synthesized with 4,4′‐dipheylmethane diisocyanate [1,1′‐methylenebis(4‐isocyanatobenzene)], 1,4‐butane diol, and 1,1,1‐trimethylol propane by a prepolymer method. The degree of microphase separation of the PUEs became weaker with increasing side group content in polymer glycols. Dynamic viscoelastic properties measurement showed reorganized‐crystallization and melting of the soft segment for the PUEs based on PTMG, PTG‐L, and PTG‐X with a lower content of the side groups, but not for a PTG‐L and PTG‐X with higher content of the side groups. Tensile testing revealed that increasing methyl group concentration made the PUEs soften and weaken. The PTMG‐based PUEs obviously exhibited strain‐induced crystallization of the soft segment chains during elongation process. In contrast, for the PTG‐L and PTG‐X‐based PUEs, crystallinity decreased with increasing side group content, and the PUEs with PTG‐L and PTG‐X with highest methyl group content did not crystallize even at a large strain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2054–2063, 2008     

Synthesis and characterization of poly(urethane-sulfone)s

Eight poly(urethane-sulfone)s were synthesized from two sulfone-containing diols, 1,3-bis(3-hydroxypropylsulfonyl)propane (Diol-333) and 1,4-bis(3-hydroxypropylsulfonyl)butane (Diol-343), and three diisocyanates, 1,6-hexamethylene diisocyanate (HMDI), 4,4′-diphenylmethane diisocyanate (MDI), and tolylene diisocyanate (TDI, 2,4- 80%; 2,6-20%). As a comparison, eight polyurethanes were also synthesized from two alkanediols, 1,9-nonanediol and 1,10-decanediol, and three diisocyanates. Diol-333 and Diol-343 were prepared by the addition of 1,3-propanedithiol or 1,4-butanedithiol to allyl alcohol and subsequent oxidation of the resulting sulfide-containing diols. The homopoly(urethanesulfone)s from HMDI and MDI are semicrystalline, and are soluble in m-cresol and hot DMF, DMAC, and DMSO. The copoly(urethane-sulfone)s from a 1/1 molar ratio mixture of Diol-333 and Diol-343 with HMDI or MDI have lower crystallinity and better solubility than the corresponding homopoly(urethane-sulfone)s. The poly(urethane-sulfone)s from TDI are amorphous, and are readily soluble in m-cresol, DMF, DMAC, and DMSO at room temperature. Differential scanning calorimetry data showed that poly(urethane-sulfone)s have higher glass transition temperatures and melting points than the corresponding polyurethanes without sulfone groups. The rise in glass transition temperature is 20–25°C while the rise in melting temperature is 46–71°C. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of hyperbranched poly(urea‐urethane)s based on AA* and B2B* monomers

Hyperbranched aromatic and aliphatic poly(urea‐urethane)s were prepared by the one‐pot method using 2,4‐toluylene diisocyanate (TDI), isophorone diisocyanate, and 2(3‐isocyanatopropyl)cyclohexyl isocyanate as AA* monomers and diethanol amine and diisopropanol amine as B₂B* monomers. The characteristics of the resulting polymers were very sensitive to slight changes in the reaction conditions, such as temperature, concentration, and type of catalyst used, as can be seen from the results of gel permeation chromatography and differential scanning calorimetry. The structures were analyzed in detail using ¹H and ¹³C NMR spectroscopy. By using model compounds, the different isomeric structures of the TDI polymers were deduced, their percentages of their linear, terminal, and dendritic subunits were calculated, and their degree of branching (DB) was determined. DB values up to 70% were reached depending on the reaction conditions and stoichiometry of the monomers. The number of terminal groups decreased significantly when dibutylamine was used to stop the reaction instead of B₂B*, indicating the presence of a significant number of unreacted isocyanate groups in the hyperbranched product when the polyaddition reaction was stopped. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3062–3081, 2004     

Polyesters containing sulfur. VIII. New benzophenone‐derivative thiopolyesterdiols synthesis and characterization. Their use for thermoplastic polyurethanes preparation

The new linear thiopolyesterdiols (PEs) containing sulfur in the main chain were synthesized by melt polycondensation of newly obtained benzophenone‐4,4′‐bis(methylthioacetic acid) with excess of 1,4‐butanediol, 1,5‐pentanediol, and 1,6‐hexanediol. All these PEs (M _n of 2000–2600) were converted to thiopoly(ester‐urethane)s (PEUs) by polyaddition reaction with hexamethylene diisocyanate or 4,4′‐diphenylmethane diisocyanate, which was carried out in melt at the ratio of NCO/OH = 1. The resulting thermoplastic PEUs were amorphous and elastomeric, with elongation at break ranging from 630 to 1200%. The polymers were characterized by Fourier transform infrared, ¹H NMR, thermogravimetric analysis, differential scanning calorimetry, and in the case of PEUs, Shore A/D hardness and tensile properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3977–3983, 2000     

Conformationally restricted linear polyurethanes from acetalized sugar‐based monomers

Linear polyurethanes based on sugar monomers having D ‐gluco, galacto, and D ‐manno configurations and their secondary hydroxyl groups protected as bicyclic acetals, have been prepared by polyaddition reaction of these diol monomers to hexamethylene diisocyanate ( HMDI ) and 4,4′‐methylene‐bis(phenyl isocyanate) ( MDI ). The new polyurethanes seem to be amorphous materials, except that obtained from 2,3:4,5‐di‐O‐methylene‐galactitol and HMDI. Weight‐average molecular weights, determined by GPC, were in the range 16,000–115,200. TGA analyses indicated that the thermal stability of these bicyclic polyurethanes is comparable to those based on the isosorbide; both the onset and the maximum rate decomposition temperatures increased significantly with respect to the polyurethanes based on acyclic sugar monomers. The presence of the acetalized alditol units in the polyurethanes also increased the T_gs as compared with their acyclic analogs. Deacetalization of the polyurethanes containing di‐O‐isopropylidene‐D ‐mannitol units yielded the polyhydroxylated polymers in good yields, without apparent degradation of the polymer chain. These hydroxylated polymers showed an enhanced hydrophilicity and degradability and lower T_gs and thermal stability than their parent acetalized polyurethanes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis,characterization, and evaluation of novel polyhydantoins as gas separation membranes

Novel polyhydantoins ( PHYs ) were synthesized from original aromatic diisocyanates and bisiminoacetates by a two‐step polycondensation procedure, which involved the cyclization of polyurea intermediates promoted by acid catalysis. The physical properties of the novel PHYs were evaluated by comparing them with a classical PHY derived from 4,4′‐methylenediphenyl diisocyanate. All PHYs were soluble and could be processed into dense films, which showed good mechanical properties (tensile strength up to 110 MPa) and thermal stability of >400 °C. High glass transition temperatures (T_gs), ranging from 260 to 410 °C, were observed. Fractional free volume (FFV) was strongly dependent on the chemical structure, and a linear correlation between gas permeability and FFV of PHYs could be found. The gas separation properties were comparable to those of the commercial polyimide Matrimid^®, with the exception of one of the PHYs which exhibited very promising properties as its gas productivity was comparable to the gas separation performance of well‐established experimental polyimides. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4052–4060     

STUDIES ON METAL-CONTAINING POLYURETHANES BASED ON DIVALENT METAL SALTS OF MONO(HYDROXYETHOXYETHYL)PHTHALATE

By reacting phthalic anhydride with excess of diethylene glycol and metal acetate, the metal salts of mono(hydroxyethoxyethyl)phthalate were prepared (metal = Cu²⁺, Mn²⁺ and Zn²⁺). Polyurethanes containing metal ions in the main chain were synthesized by reacting hexamethylene diisocyanate (HMDI) or tolulylene 2,4-diisocyanate (TDI) with Cu²⁺, Mn²⁺ and Zn²⁺ salts of mono(hydroxyethoxyethyl)phthalate using di-n-butyltin dilaurate (DBTDL) as catalyst. The prepared monomers and polyurethanes were characterized by FT-IR, ¹H-NMR, ¹³C-NMR, UV spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), elemental analysis, solubility and viscosity studies. The antibacterial activity of these polyurethanes have also been investigated using agar diffusion method.     

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     

Effect of the terminal substituent of azobenzene on the properties of ABA triblock copolymers via atom transfer radical polymerization

The effect of the terminal substituent of azobenzene on the properties of ABA triblock copolymers was investigated. For this study, three kinds of azobenzene‐containing monomers with different terminal substituents—6‐[4‐(4‐methoxyphenylazo)phenoxy] hexyl methacrylate, 6‐[4‐(4‐ethoxyphenylazo)phenoxy]hexyl methacrylate, and 6‐[4‐(4‐nitrophenylazo)phenoxy]hexyl methacrylate—were used to synthesize ABA triblock copolymers PMMAzo₂₅–PEG₁₃–PMMAzo₂₅/PMMAzo₁₂–PEG₁₃–PMMAzo₁₂, PEMAzo₁₄–PEG₁₃–PEMAzo₁₄, and PNMAzo₁₄–PEG₁₃–PNMAzo₁₄, respectively, by atom transfer radical polymerization (PMMAzo is poly{6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl methacrylate}, PEMAzo is poly{6‐[4‐(4‐ethoxyphenylazo)phenoxy]hexyl methacrylate}, and PNMAzo is poly{6‐[4‐(4‐nitrophenylazo)phenoxy]hexyl methacrylate}). These copolymers were characterized with ¹H NMR spectroscopy and gel permeation chromatography and exhibited controlled molecular weights and narrow molecular weight distributions. Differential scanning calorimetry and polarizing optical microscopy showed that these copolymers had mesophases. PMMAzo₂₅–PEG₁₃–PMMAzo₂₅ and PMMAzo₁₂–PEG₁₃–PMMAzo₁₂ had a smectic mesophase and a nematic mesophase, whereas both PEMAzo₁₄–PEG₁₃–PEMAzo₁₄ and PNMAzo₁₄–PEG₁₃–PNMAzo₁₄ had a nematic mesophase. This demonstrated that the liquid‐crystalline properties of these copolymers highly depended on the terminal substituent of azobenzene. The photoresponsive behavior of these copolymers was also investigated in tetrahydrofuran solutions, and the influence of the terminal substituents attached to azobenzene was studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5190–5198, 2007     

Nylon 6–polyisobutylene sequential copolymers. II. Synthesis,characterization, and morphology of di-, tri-, and radial block copolymers

Nylon 6–PIB diblock, triblock, and tristar radial block copolymers have been synthesized from telechelic hydroxyl-terminated polyisobutylene, PIB(OH)_n (n = 1,2,3), by conversion of this prepolymer with hexamethylene diisocyanate (HMDI), toluene diisocyanate (TDI), N-chlorocarbonyl diisocyanate (NCCI), and oxalyl chloride (OxCl) and using the resulting materials as macroactivators for anionic caprolactam polymerization. Prepolymers with molecular weights from 6000 to 38,000 have been employed. Derivatization with NCCI and subsequent anionic caprolactam polymerization gave highest yields and blocking efficiencies. The block copolymers have been characterized by molecular weight and composition. In addition to the expected T_g and T_m characteristics of long PIB and nylon 6 segments, DSC studies showed an intermediate glass transition at ca. ?20°C. Transmission electron microscopy of di-, tri-, and radial blocks show increasing segregation and orientation of rubbery/crystalline domains. Tensile strengths and elongations of the block copolymers range from 16.5 to 41 MPa and 15 to 30%, respectively, and stress-strain diagrams show the effect of block architecture on these properties.     

Reversibly light‐responsive biodegradable poly(carbonate) micelles constructed via CuAAC reaction

Light‐responsive poly(carbonate)s PEG₁₁₃‐b‐PMPC_n‐SP were synthesized via copper catalyzed azide‐alkyne cycloaddition reaction between azide‐modified spiropyran (SP‐N₃) and amphiphilic copolymer PEG₁₁₃‐b‐PMPC_n. PEG₁₁₃‐b‐PMPC₂₅‐SP can self‐assemble to biocompatible micelles with an average diameter of ～96 nm and a critical aggregation concentration of 0.0148 mg mL^?1. Under 365 nm UV light irradiation, the characteristic absorption intensity of merocyanine (MC) progressively increased and most of the micellar aggregations were disrupted within 10 min, suggesting the completion of the transformation of hydrophobic SP to hydrophilic MC. Subsequent exposuring the micelles to 620 nm visible light, spherical micelles aggregated again. The light‐controlled release and re‐encapsulation behaviors of coumarin 102‐loaded micelles were further investigated by fluorescence spectroscopy. This study provides a convenient way to construct smart poly(carbonate)s nanocarriers for controlled release and re‐encapsulation of hydrophobic drugs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 750–760     

Thermal behaviors and characteristics of polylactide/poly(butylene succinate) blend films via reactive compatibilization and plasticization

Polylactide (PLA)/poly(butylene succinate) (PBS) blend films modified with a compatibilizer and a plasticizer were hot‐melted through a twin screw extruder and prepared by hydraulic press. Toluene diisocyanate (TDI) and polylactide‐grafted‐maleic anhydride (PLA‐g‐MA) were used as compatibilizers, while triethyl citrate and tricresyl phosphate acted as plasticizers. The effects of the type and content of compatibilizer and plasticizer on the mechanical characteristics, thermal properties, crystallization behavior, and phase morphology of the PLA/PBS blend films were investigated. Reactive compatibilization at increasing levels of TDI improved the compatibility of the PLA and PBS, affecting the toughness of the films. As evidenced by scanning electron microscope, the addition of TDI enhanced the interfacial adhesion of the blends, leading to the appearance of many elongated fibrils at the fracture surface. Furthermore, PLA/PBS blending with both TDI and PLA‐g‐MA led to an acceleration of the cold crystallization rate and an increment of the degree of crystallinity ( ). Toluene diisocyanate could be a more effective compatibilizer than PLA‐g‐MA for PLA/PBS blend films. The synergistic combination of compatibilizer and plasticizer brought a significant improvement in elongation at break and tensile‐impact toughness of the PLA/PBS blends, compared with neat PLA. Their failure mode changed from brittle to ductile due to the improved compatibility and molecular segment mobility of the PLA and PBS phases. Differential scanning calorimeter results revealed that the plasticizers triethyl citrate and tricresyl phosphate changed the thermal behavior of T_cc and T_m, affecting α′ and α crystal formations. However, these plasticizers only slightly improved the thermal stability of the films.