Effect of chain extender structure on the properties and morphology of polyurethanes based on H12MDI and mixed macrodiols (PDMS–PHMO)

The effect of chain extender structure on properties and morphology of α,ω‐bis(6‐hydroxyethoxypropyl) polydimethylsiloxane (PDMS) and poly(hexamethylene oxide) (PHMO) mixed macrodiol‐based aliphatic polyurethane elastomers was investigated using tensile testing, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). All polyurethanes were based on 50 wt % of hard segment derived from 4,4′‐methylenecyclohexyl diisocyanate (H₁₂MDI) and a chain extender mixture. 1,4‐Butanediol was the primary chain extender, while one of 1,3‐bis(4‐hydroxybutyl)tetramethyldisiloxane (BHTD), 1,3‐bis(3‐hydroxypropyl)tetramethyldisiloxane (BPTD), hydroquinonebis(2‐hydroxyethyl)ether (HQHE), 1,3‐bis(3‐hydroxypropyl)tetramethyldisilylethylene (HTDE), or 2,2,3,3,4,4‐hexafluoro‐1,5‐pentanediol (HFPD) each was used as a secondary chain extender. Two series of polyurethanes containing 80 : 20 (Series A) and 60 : 40 (Series B) molar ratios of primary and secondary chain extenders were prepared using one‐step bulk polymerization. All polyurethanes were clear and transparent and had number‐average molecular weights between 56,000 and 122,100. Incorporation of the secondary chain extender resulted in polyurethanes with low flexural modulus and high elongation. Good ultimate tensile strength was achieved in most cases. DSC and DMTA analyses showed that the incorporation of a secondary chain extender disrupted the hard segment order in all cases. The highest disruption was observed with HFPD, while the silicon‐based chain extenders gave less disruption, particularly in Series A. Further, the silicon chain extenders improved the compatibility of the PDMS soft segment phase with the hard segment, whereas with HFPD and HQHE, this was not observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2979–2989, 1999     

Synthesis and physical properties of H12MDI-based polyurethane resins

This paper described the synthesis of four types of polyurethanes by using diisocyanato dicyclohexylmethane (H₁₂MDI) as the hard segment and poly hexamethylene carbonate diol, polybutylene adipate diol, poly(hexamethylene diol/neopentyl glycol)-based copolyester diol, or poly hexamethylene diol/hexamethylene carbonate)-based copolyester/carbonate diol as the corresponding soft segment. The spectral analysis, thermal studies (differential scanning calorimetry and dynamic mechanical analysis), tensile strength-elongation relationship, and water vapor permeability of these samples were investigated. The results of these studies showed that the phase separation extent of the four types of polyurethanes displayed the following order: ESBA (polybutylene adipate-based polyurethane) > ECHH (co-polyester / carbonate-based polyurethane) > ESHN (copolyester diol-based polyurethane) > CAHC (polyhexamethylene carbonate-based polyurethane). The water vapor permeability of the cast films increased with the increase of the phase separation extent, in which the polyester-based polyurethane (sample ESBA) displayed the highest water vapor permeability. In terms of tensile strength-elongation property, the polycarbonate diol based polyurethane displayed higher tensile strength but lower elongation than polyester-based polyurethanes.     

Effect of soft-segment CH2/O ratio on morphology and properties of a series of polyurethane elastomers

A series of six thermoplastic polyurethane elastomers were synthesized from a 4,4′-methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender, with poly(ethyleneoxide) (PEO), poly(tetramethylene oxide) (PTMO), poly(hexamethylene oxide) (PHMO), poly(octamethylene oxide) (POMO), poly(decamethylene oxide) (PDMO), and poly(1,6-hexyl carbonate)diol (PCDO) macrodiol soft segments. The soft-segment molecular weights employed were similar (approximately 1000 g/mol) and each polyurethane contained 55% (w/w) of the soft-segment macrodiol. Differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), wide-angle X-ray diffraction (WAXD), and Fourier transform infrared spectroscopy (FTIR) techniques were employed to characterize the morphology. Tensile and Shore hardness tests were also performed. Materials were tested in the as-molded, solvent-cast, and annealed states. It was found that the polyurethanes produced from macrodiols with the highest CH₂/O ratio displayed greater hard-domain crystallinity, a higher degree of phase separation, and the greatest hardness, stiffness, and opacity. POMO- and PDMO-based polymers displayed evidence of paracrystallinity in the soft domains. The PCDO-based material displayed a higher degree of phase mixing compared to the polyether-based materials. Annealing increased hard-domain crystallinity in all the polyether-based materials. The solvent-cast POMO- and PDMO-based materials had poor mechanical properties and were difficult to cast. The materials containing macrodiols with the lowest CH₂/O ratio were more readily solvent-cost and produced strong, useful films. Morphologies of the solvent-cast materials differed greatly from those of the molded materials. © 1996 John Wiley & Sons, Inc.     

Low‐modulus siloxane‐based polyurethanes. I. Effect of the chain extender 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD) on properties and morphology

A series of eight polyurethane elastomers was prepared using a two‐step bulk polymerization procedure to investigate the effect of the siloxane chain extender 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD) on polyurethane properties and morphology. All polyurethanes were based on 40 wt % hard segment derived from 4,4′‐methylenediphenyl diisocyanate (MDI) and a mixture of 1,4‐butanediol (BDO) and BHTD in varying molar ratios. The soft segment was based on an 80 : 20 (w/w) mixture of the macrodiols α,ω‐bis(6‐hydroxyethoxypropyl)polydimethylsiloxane (PDMS, MW 965) and poly(hexamethylene oxide) (PHMO, MW 714). Polyurethanes were characterized by size‐exclusion chromatography, tensile testing, differential scanning calorimetry, dynamic mechanical thermal analysis, and FTIR spectroscopy. Clear and transparent polymers were produced in all cases with number‐average molecular weights in the range of 90,000 to 111,000. The ultimate tensile strength decreased only slightly (15%), but Young's modulus and flexural modulus decreased by 76 and 72%, respectively, compared with that of the pure BDO extended polyurethanes as the amount of BHTD was increased to 40 mol %. This change resulted in “softer” and more elastic polyurethanes. Polyurethanes with BHTD contents above 40 mol % were more elastic but had poor tensile and tear strengths. A 60 : 40 molar ratio of BDO : BHTD produced a “soft” polyurethane, which combined good tensile strength and flexibility. The DSC and DMTA results confirmed that the incorporation of BHTD as part of the hard segment yielded polyurethanes with improved compatibility between hard and soft segments. IR data indicated that the amount of hard segments soluble in the soft‐segment phase increased with increasing BHTD, contributing to the improved phase mixing. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 736–746, 2002     

A novel side chain liquid crystalline polyurethane

Summary Side chain liquid crystalline polyurethanes (SCLP) without flexible spacer were synthesized by a two step block copolymerization reaction. The polyurethanes were based on azobenzene-type mesogenic diol chain extender (DR-19), a poly(tetramethylene oxide) (PTMO) soft segment, and different diisocyanates, including 4,4-diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). The polyurethane samples obtained from DR-19 or DR-19 and PTMO with HDI had mesomorphic phases as determined by DSC and polarizing microscopy. Received: 19 March 1998/Revised version: 27 May 1998/Accepted: 17 June 1998     

Poly(dimethylsiloxane)/poly(hexamethylene oxide) mixed macrodiol based polyurethane elastomers. I. Synthesis and properties

The compatibilizing effect of poly(hexamethylene oxide) (PHMO) on the synthesis of polyurethanes based on α,ω‐bis(6‐hydroxyethoxypropyl) poly(dimethylsiloxane) (PDMS) was investigated. The hard segments of the polyurethanes were based on 4,4′‐methylenediphenyl diisocyanate (MDI) and 1,4‐butanediol. The effects of the PDMS/PHMO composition, method of polyurethane synthesis, hard segment weight percentage, catalyst, and molecular weight of the PDMS on polyurethane synthesis, properties, and morphology were investigated using size exclusion chromatography, tensile testing, and differential scanning calorimetry (DSC). The large difference in the solubility parameters between PDMS and conventional reagents used in polyurethane synthesis was found to be the main problem associated with preparing PDMS‐based polyurethanes with good mechanical properties. Incorporation of a polyether macrodiol such as PHMO improved the compatibility and yielded polyurethanes with significantly improved mechanical properties and processability. The optimum PDMS/PHMO composition was 80 : 20 (w/w), which yielded a polyurethane with properties comparable to those of the commercial material Pellethane™ 2363‐80A. The one‐step polymerization was sensitive to the hard segment weight percentage of the polyurethane and was limited to materials with about a 40 wt % hard segment; higher concentrations yielded materials with poor mechanical properties. A catalyst was essential for the one‐step process and tetracoordinated tin catalysts (e.g., dibutyltin dilaurate) were the most effective. Two‐step bulk polymerization overcame most of the problems associated with reactant immiscibility by the end capping of the macrodiol and required no catalysts. The DSC results demonstrated that in cases where poor properties were observed, the corresponding polyurethanes were highly phase separated and the hard segments formed were generally longer than the average expected length based on the reactant stoichiometry. Based on these results, we postulated that at low levels (∼ 20 wt %) the soft segment component derived from PHMO macrodiol was concentrated mainly in the interfacial regions, strengthening the adhesion between hard and soft domains of PDMS‐based polyurethanes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 2026–2040, 2000     

The influence of composition ratio on the morphology of biomedical polyurethanes

Two series of thermoplastic polyurethane elastomers were synthesized from 4,4′‐methylenediphenyl diisocyanate (MDI), 1,4‐butanediol (BDO) chain extender, and each of poly(tetramethylene oxide) (PTMO) and poly(hexamethylene oxide) (PHMO) macrodiols. The PTMO and PHMO molecular weights were kept constant at 993 and 852 g/mol, respectively. In the PTMO‐based series, the composition ratio was varied between 48 and 58% (w/w) of macrodiol; 2 commercially available PTMO‐based polymers were also included. These were Pellethane 2363 80A® and its harder counterpart, Pellethane 2363 55D®. In the PHMO‐based series, the composition ratio was varied between 50 and 60% (w/w) of macrodiol. The materials were characterized by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS). Mechanical performance was also assessed by tensile testing, stress hysteresis, and hardness testing. Altering the composition ratio had a similar effect on morphology and properties for both the PTMO and PHMO‐based series. An increase in hard segment content was associated with increased hard microdomain crystallinity, hardness, and stiffness. In both series, he beginning of hard microdomain interconnectivity was observed at a composition ratio of 52% soft segment. That is to say, for the processing and annealing conditions employed, macrodiol contents of 52% and below began to produce continuous, rather than discrete, hard microdomains. Pellethane 80A® was shown to have a discrete hard microdomain morphology, while Pellethane 55D® was shown to incorporate interconnecting hard microdomains. It is suggested that the superior biostability performance of Pellethane 55D relative to Pellethane 80A may be related to its interconnecting hard microdomain texture. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 937–952, 1999     

Low‐modulus siloxane–polyurethanes. Part II. Effect of chain extender structure on properties and morphology

A series of six polyurethanes were prepared to study the effect of silicon chain extender structure on properties and morphology of siloxane–polyurethanes. Polyurethanes were prepared by a two‐step bulk polymerization without a catalyst. The soft segment of the polyurethanes was based on an 80:20 (w/w) mixture of α,ω‐bis(6‐hydroxyethoxypropyl) polydimethylsiloxane (PDMS, MW 966) and poly(hexamethylene) oxide (MW 714). The hard segment was based on 4,4′‐methylenediphenyl diisocyanate (MDI) and a 60:40 molar mixture of 1,4‐butanediol (BDO) and a silicon chain extender. Silicon chain extenders (SCE) investigated were 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD), 1,3‐bis(3‐hydroxypropyl)1,1,3,3‐tetramethyldisiloxane (BPTD), 1,4‐bis(3‐hydroxypropyl)1,1,3,3‐tetramethyldisilylethylene (HTDE), 1,3‐bis(6‐hydroxyethoxypropyl)1,1,3,3‐tetramethyldisiloxane (BETD). All polyurethanes were clear and transparent with number average molecular weights between 72,000 to 116,000. Incorporation of the silicon chain extender resulted in polyurethanes with low‐modulus and high elongation. This was achieved without significant compromise in ultimate tensile strength in all cases, except BETD. Differential scanning calorimetry (DSC) results showed that the silicon chain extenders did not significantly disrupt the hard segment crystallinity, but exhibited a unique morphological feature where SCE‐based hard segments formed separate domains, which may be the primary reason for achieving low modulus without significant compromise in strength. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1092–1100, 2003     

Properties of crosslinked blends of pellethene and multiblock polyurethane containing poly(ethylene oxide) for biomaterials

A series of multiblock polyurethanes, containing various poly(ethylene oxide) (PEO; number‐average molecular weight = 400–3400) contents (0–80 wt %) and prepared from hexamethylene diisocyanate/PEO/poly(dimethylsiloxane) diol/polybutadiene diol/1,4‐butanediol, were used as modifying additives (30 wt %) to improve the properties of biomedical‐grade Pellethene. Different molecular weights of PEO were used to keep poly(ethylene glycol) at a fixed molar content, if possible, although the PEO content, related to the PEO block length in the multiblock polyurethanes, was varied from 0 to 80 wt %. The hydrophilic PEO component was introduced through the addition of PEO‐containing polyurethanes and dicumyl peroxide as a crosslinking agent in a Pellethene matrix. As the PEO content (PEO block length) increased, the hydrogen‐bonding fraction of the crosslinked Pellethene/multiblock polyurethane blends increased, and this indicated an increase in the phase separation with an increase in the PEO content in the crosslinked Pellethene/multiblock polyurethane blends. According to electron spectroscopy for chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked Pellethene/multiblock polyurethane blends increased remarkably with increasing PEO content. The water contact angle of the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased with increasing PEO content. The water absorption and mechanical properties (tensile modulus, strength, and elongation at break) of the crosslinked Pellethene/multiblock polyurethane blend films increased with increasing PEO content. The platelet adhesion on the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased significantly with increasing PEO content. These results suggest that crosslinked Pellethene/multiblock polyurethane blends containing the hydrophilic component PEO may have potential for biomaterials that come into direct contact with blood. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2348–2357, 2004     

Synthesis,characterization, and stability of poly[(alkylene oxide) ester] thermoplastic elastomers

Poly(ether ester) block copolymers were prepared using a transesterification/polycondensation bulk synthesis with systematic control of the terephthalic acid/butane-diol aromatic diester block (`hard segment') and with poly(tetramethylene oxide) [PTMO], poly(hexamethylene oxide) [PHMO], or poly(decamethylene oxide) [PDMO] poly(alkylene oxide) soft segments. The respective number average molecular weights were 980, 930, and 940 Da. A series of the poly(ether ester)s with hard segment fractions of 25, 29, 37, and 51% were prepared. One example of the PDMO polyester was prepared at a 51% hard segment fraction. The polyesters were characterized using viscometry, gel permeation chromatography, ¹H-NMR spectroscopy, differential scanning calorimetry, and tensile testing. The novel poly(ether ester)s, the PTMO polyester, and the commercial control, Hytrel® 4056, were compared for their resistance to degradation in a 50% aqueous hydrogen peroxide solution at 37°C, boiling water buffered at pH 1 and 13, an oxygen stream at 200°C, and a nitrogen stream at 200°C. The Hytrel® 4056 and the PTMO polyesters fragmented in hydrogen peroxide within 24 h while the PHMO and PDMO polyesters were much less degraded. Resistance to hydrolytic and thermal degradation increased as the ratio of aliphatic methylene to ether increased: PTMO < PHMO < PDMO. Samples containing higher hard segment fractions demonstrated improved resistance to hydrolysis. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1319–1332, 1997     

Synthesis of biodegradable amphiphilic thermo‐responsive multiblock polycarbonate and its self‐aggregation behavior in aqueous solution

Amphiphilic thermo‐responsive multiblock polycarbonates consisting of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) were facilely synthesized using triphosgene as coupling agent. The structures and molecular characteristics of the polycarbonates were confirmed by ¹H‐NMR, FT‐IR and Gel permeation chromatography (GPC). The crystallization behavior and thermal properties of the polycarbonates were studied using X‐ray diffraction (XRD), Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface tension measurements confirmed that the critical micelles concentration of polymeric micelles were concentration ranges, which varied from about 2–70 mg/L to 5–40 mg/L with increasing PEO/PPO composition ratio from 0.8 to 1. Dynamic light scattering (DLS) experiments showed bimodal size distributions, the aggregates size increased with increasing the concentration of the polycarbonates aqueous solutions. The size of the aggregates acquired from TEM was smaller than that from DLS owing to the fact that TEM gave size of the aggregates in dry state rather than the hydrodynamic diameter. The degradation process revealed that the degradation rate of the aggregates could be accelerated with an increase in temperature. Moreover, the more the polycarbonate was hydrophilic, the faster was its degradation. Rheological measurements suggested that these multiblock polycarbonates were thermo‐responsive and by regulating the PEO/PPO composition ratio they could form a gel at 37°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Temperature sensitive water vapour permeability and shape memory effect of polyurethane with crystalline reversible phase and hydrophilic segments

Polyurethanes based on poly(caprolactone) (PCL) diol, hexamethylene diisocyanate, 4,4′‐diphenylmethane diisocyanate and hexamethylene diamine were modified by hydrophilic segments, diol‐terminated poly(ethylene oxide) or dimethylol propionic acid (DMPA). Differential scanning calorimetry, dynamic mechanical tests, tensile tests, and measurement of water vapour permeability were carried out to characterize these polyurethanes. Temperature sensitive water vapour permeability, that is, the abrupt increase of water vapour permeability at the melting temperature of the PCL phase, was enhanced by modification with hydrophilic segments. Fatigue in shape memory effects was minimized by introducing some amount of DMPA units into the polyurethane chain. © 2000 Society of Chemical Industry     

Microdomain composition and properties differences of biodegradable polyurethanes based on MDI and HDI

The study of the effect of the diisocyanate structure on the microstructure and macroscopic properties of polyurethanes was the main aim of this work. Biodegradable segmented thermoplastic elastomeric polyurethanes based on a poly(hexamethylene carbonate‐co‐caprolactone)diol (PHM‐co‐PCL) as soft segment were synthesized using 1,4‐butanediol (BD) as chain extender and both 4,4′‐diphenylmethane diisocyanate (MDI) and 1,6‐hexamethylene diisocyanate (HDI) as components of the hard segment by the two shoot synthesis procedure. Microphase structure and properties were analyzed using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) as complementary techniques, used to characterize thermal transitions of the polyurethanes and to assign them to determinate functional groups interactions. Gaussian deconvolution technique was used to decompose carbonyl region in four peaks and to study the hydrogen bonding within the different polyurethanes. Both DSC and FTIR showed that MDI‐based biodegradable polyurethanes were less phase segregated than to those based on HDI, and thus that diisocyanate structure has an important role on microdomain composition and polyurethanes properties. Macroscopic properties as hardness and water‐polymer contact angles are related to polyurethanes microphase compositions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Preparation of poly(IPDI‐PTMO‐siloxanes) and influence of siloxane structure on reactivity and mechanical properties

Siloxane‐modified polyurethanes were prepared through isophorone diisocyanates (IPDI), poly(tetramethylene oxide) (PTMO), and siloxanes. IPDI served as the hard segment in the structure. Both PTMO and siloxanes were diols and served as the soft segments. In addition, different chemical structures of siloxanes were used, in which siloxane chains would remain in the main chain of polyurethanes (PU) or become the side chain of PU. First, the reactivities of PTMO and siloxanes to react with IPDI in bulk system were studied through DSC, in which the reaction heat was related to their reactivities. Copolymerization of IPDI, PTMO, and siloxanes in bulk were also studied. The results showed that hydrophobicity and steric hindrance of siloxane diols led to their low reactivities. Next, a series of siloxane‐modified PU in toluene solvent were synthesized, and the conversion of NCO groups was determined by the method of chemical titration. In the synthesis of PU copolymers in a solution polymerization, because of low reactivity of siloxanes, a two‐step procedure was adopted. The siloxane diol was first reacted with IPDI in toluene to form NCO‐terminated prepolymer. Then PTMO was added to form final PUcopolymers. The addition of side‐chain siloxanes resulted in PU copolymers with higher molecular weight than main‐chain siloxanes. Both main‐chain and side‐chain siloxanes increased the elongation at break and tensile strength of final PU copolymers. The microphase‐separation of siloxane segments was observed by SEM, which was the main cause for the improved mechanical properties. POLYM. ENG. SCI., 47:625–632, 2007. © 2007 Society of Plastics Engineers.     

New thermoplastic segmented polyurethanes with hard segments derived from 4,4′‐diphenylmethane diisocyanate and methylenebis(1,4‐phenylenemethylenethio)dialcanols

New thermoplastic poly(ether–urethane)s and poly(carbonate–urethane)s were synthesized by a one‐step melt polymerization from poly(oxytetramethylene) diol (PTMO) and poly(hexane‐1,6‐diyl carbonate) diol (PHCD) as soft segments, 4,4′‐diphenylmethane diisocyanate, and 2,2′‐[methylenebis(1,4‐phenylenemethylenethio)]diethanol, 3,3′‐[methylenebis(1,4‐phenylenemethylenethio)]dipropan‐1‐ol or 6,6′‐[methylenebis(1,4‐phenylenemethylenethio)]dihexan‐1‐ol as unconventional chain extenders. The effects of the kind and amount of the polymer diol and chain extender used on the structure and properties of the polymers were studied. The polymers were examined by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction analysis, atomic force microscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), TGA coupled with FTIR spectroscopy, and Shore hardness and tensile testing. The obtained high‐molecular‐weight polymers showed elastomeric or plastic properties. Generally, the PTMO‐based polymers exhibited significantly lower glass‐transition temperatures (up to ?48.1 vs ?1.4°C), a higher degree of microphase separation, and ordering in hard‐segment domains in comparison with the corresponding PHCD‐based ones. Moreover, it was observed that the polymers with the PTMO soft segments showed poorer tensile strengths (up to 36.5 vs 59.6 MPa) but higher elongations at break. All of the polymers exhibited a relatively good thermal stability. Their temperatures of 1% mass loss were in the range 270–320°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and surface mobility of segmented polyurethanes with fluorinated side chains attached to hard blocks

Novel polyurethanes with fluorinated side chains attached to hard blocks were synthesized and characterized by NMR, mass spectroscopy, DSC and gel permeation chromatography (GPC). A unique chain extender, 3-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-octyloxy)-propane-1,2-diol (PFOPDOL) was prepared from 3-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-octyloxymethyl)-oxirane (PDFOMO) by reacting it with diluted perchloric acid. Poly(ether urethane)s and poly(carbonate urethane)s containing various amounts of the chain extender with fluorinated side chains were then synthesized using methylenebis(phenylene isocyanate) (MDI), polytetramethyleneoxide (PTMO), poly(1,6-hexyl-1,5-pentylcarbonate) diol (PHPCD), 1,4-butandiol (BDO) and PFOPDOL. Mechanical properties of the polyurethanes were characterized by Instron. Surface properties were characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Results from GPC and Instron studies indicated that fluorinated polyurethanes with high molecular weights and good mechanical properties were obtained. Results from XPS and contact angle studies indicated that the surface of fluorinated polyurethanes were very nonpolar due to migration of fluorinated side chains to the surface.     

Aggregation phenomena of amphiphilic UVB absorptive oligoesters containing p‐alkoxycinnamate and poly(ethylene oxide) blocks

The synthesis of new amphiphilic oligoesters containing a hydrophobic block based on p‐alkoxycinnamate and hydrophilic poly(ethylene oxide) is reported. Two hydrophobic monomers, 1,2‐(bis(4‐(2‐carboxyvinyl)phenoxy))ethane ( M2 ) and 1,12‐(bis(4‐(2‐carboxyvinyl) phenoxy))dodecane ( M12 ), were synthesized. Four oligoesters, poly((1,2‐(bis(4‐(2‐carboxyvinyl)phenoxy))ethane) ‐co‐(poly(ethylene oxide)200)) ( P2‐200 ), poly((1,2‐(bis(4‐(2‐carboxyvinyl)phenoxy))ethane)‐co‐(poly(ethylene oxide) 400)) ( P2‐400 ), poly((1,12‐(bis(4‐(2‐carboxyvinyl)phenoxy)) dodecane)‐co‐(poly(ethylene oxide)400)) ( P12‐400 ), and poly((1,12‐(bis(4‐(2‐carboxyvinyl)phenoxy))dodecane)‐co‐ (poly(ethylene oxide)1000)) ( P12‐1000 ) were then constructed by reacting the M2 or M12 with poly(ethylene oxide) (PEO) with lengths of ～ 4 (PEO 200), ～ 10 (PEO 400), or ～ 23 (PEO1000) units using multiple esterifications. These oligoesters possess UVB absorption properties and show good solubility in various organic solvents. Self‐assembly of the oligoesters into aqueous spherical colloids could be induced through an acetone to water solvent displacement technique. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(trimethylene terephthalate‐block‐tetramethylene oxide) elastomer/single‐walled carbon nanotubes nanocomposites: Synthesis,structure, and properties

Nanocomposites based on poly(trimethylene terephthalate)‐block‐poly(tetramethylene oxide) (PTT‐PTMO)‐segmented copolymer and COOH‐functionalized single‐walled carbon nanotubes (SWCNTs) were prepared by in situ polymerization method. The obtained nanocomposites were characterized by thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry (DSC), DMTA, wide‐angle x‐ray scattering (WAXS), small‐angle X‐ray scattering, and tensile testing. The nanocomposites with low SWCNTs loading (<0.5 wt %) shows uniform dispersion of CNT in polymer matrix. As the SWCNTs loading in the nanocomposites increase, the significant improvement of thermo‐oxidative stability was observed. It was found that the nanocomposites have slightly higher degree of crystallinity (determined by DSC and WAXS) of poly(trimethylene terephthalate) (PTT) hard phase than neat PTT‐PTMO copolymer. The melting point of PTT hard phase and glass transition temperature of poly(tetramethylene oxide)‐rich phase were not affected by the presence of CNTs in polymer matrix. The SWCNTs played a role as nucleating agent in PTT‐PTMO matrix, which led to increase in the crystallization rate. Tensile tests showed that the tensile strength of the nanocomposites with 0.05–0.3 wt % loading of SWCNTs have improved tensile strength in comparison to the neat PTT‐PTMO copolymer without reduction elongation at break. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane). II. Physical properties and bacterial adhesion

To investigate the effects of polymer chemistry and topology on physical properties and bacterial adhesion, various hydrogels composed of short hydrophilic [poly(ethylene oxide) (PEO)] and hydrophobic blocks were synthesized by polycondensation reactions. Differential scanning calorimetry and X‐ray diffraction analysis confirmed that all of the hydrogels were strongly phase‐separated due to incompatibility between PEO and hydrophobic blocks such as poly(tetramethylene oxide) (PTMO) and poly(dimethyl siloxane) (PDMS). The crystallization of PEO in the hydrogels was enhanced by the incorporation of longer PEO chains, the adoption of PDMS as a hydrophobic block, and the grafting of monomethoxy poly(ethylene oxide) (MPEO). Compared to Pellethane, the control polymer, the hydrogels exhibited higher Young's moduli and elongations at break, which was attributed to the crystalline domains of PEO and the flexible characteristics of the hydrophobic blocks. The mechanical properties of the hydrogels, however, significantly deteriorated when they were hydrated in distilled water; this was primarily ascribed to the disappearance of PEO crystallity. The water capacity of hydrogels at 37°C in phosphate‐buffered saline (PBS) (pH = 7.4) was dominantly dependant on PEO content, which also influenced the thermonegative swelling behavior. From the bacterial adhesion tests, it was evident that both S. epidermidis and E. coli adhered to Pellethane much greater than to the hydrogels, regardless of the preadsorption of albumin. Better resistance to bacterial adhesion was observed in hydrogels with longer PEO chains, with PTMO as a hydrophobic block, and with MPEO grafts. The least bacterial adhesion for both species was achieved on MPEO_2k–PTMO, a hydrogel with MPEO grafts. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1505–1514, 2003     

PPO–PC block‐copolymers used as compatibilizers in PS/PC blends

Block‐copolymers containing poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and polycarbonate of bisphenol A (PC) segments were employed as compatibilizers in polystyrene (PS)/PC blends. Block‐copolymers were prepared starting from oligomeric diols‐terminated PPO and PC. The poly(phenylene ethers) was obtained by oxidative coupling of 2,6‐dimethyl‐phenol in presence of tetramethyl bisphenol A. The copolymers were obtained with a chain extension reaction between the starting oligomers using bischloroformate of bisphenol A or phosgene as coupling agent. PS/PC blends, cast from chloroform solutions or mixed by melt, were studied by differential scanning calorimeter (DSC), dynamic‐mechanical thermal analysis (DMTA), and optical microscopy (OP). The thermal and morphological analyses showed a clear compatibilization effect between PS and PC, if PPO–PC copolymer is added when blending is performed in the melt; in addition, also mechanical properties are increased when compared with blends without PPO–PC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4654–4660, 2006