Effect of diisocyanate on pyridine containing shape memory polyurethanes based on N,N‐bis(2‐hydroxylethyl)isonicotinamide

This article demonstrates a comparative investigation about the effect of diisocyanate on pyridine containing shape memory polyurethanes (Py‐SMPUs), which are synthesized with N,N‐bis(2‐hydroxylethyl)isonicotinamide (BINA) and four different diisocyanates: 1,6‐hexanediisocyante (HDI), isophorone diisocyanate (IPDI), methylene diphenyl diisocyanate (MDI), and tolylene diisocyanate (TDI). Results show that all BINA–SMPU systems have amorphous reversible phase. Comparatively, the MDI–BINA and TDI–BINA systems show higher T_g; and the HDI–BINA and IPDI–BINA systems show better thermal stability. In addition, the HDI–BINA and the IPDI–BINA systems exhibit good thermal‐induced shape memory effect and good moisture‐sensitive shape memory effect due to their better moisture absorption properties. Particularly, the HDI–BINA system has better response speed and better shape recovery. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40721.     

Thermomechanical characteristics of benzoxazine–urethane copolymers and their carbon fiber‐reinforced composites

Copolymers of polybenzoxazine (BA‐a) and urethane elastomer (PU) with three different structures of isocyanates [i.e., toluene diisocyanate (TDI), diphenylmethane diisocyanate, and isophorone diisocyanate], were examined. The experimental results reveal that the enhancement in glass transition temperature (T_g) of BA‐a/PU copolymers was clearly observed [i.e., T_g of the BA‐a/PU copolymers in 60 : 40 BA‐a : PU system for all isocyanate types (T_g beyond 230°C) was higher than those of the parent resins (165°C for BA‐a and ?70°C for PU)]. It was reported that the degradation temperature increased from 321°C to about 330°C with increasing urethane content. Furthermore, the flexural strength synergism was found at the BA‐a : PU ratio of 90 : 10 for all types of isocyanates. The effect of urethane prepolymer based on TDI rendered the highest T_g, flexural modulus, and flexural strength of the copolymers among the three isocyanates used. The preferable isocyanate of the binary systems for making high processable carbon fiber composites was based on TDI. The flexural strength of the carbon fiber‐reinforced BA‐a : PU based on TDI at 80 wt % of the fiber in cross‐ply orientation provided relatively high values of about 490 MPa. The flexural modulus slightly decreased from 51 GPa for polybenzoxazine to 48 GPa in the 60 : 40 BA‐a : PU system. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Shape memory effect of poly(L‐lactide)‐ based polyurethanes with different hard segments

A series of biodegradable polylactide‐based polyurethanes (PLAUs) were synthesized using PLA diol (M_n = 3200) as soft segment, 4,4′‐diphenylmethane diisocyanate (MDI), 2,4‐toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI) as hard segment, and 1,4‐butanediol as chain extender. The structures and properties of these PLAUs were studied using infrared spectroscopy, differential scanning calorimetry, tensile testing, and thermomechanical analysis. Among them, the MDI‐based PLAU has the highest T_g, maximum tensile strength, and restoration force, the TDI‐based PLAU has the lowest T_g, and the IPDI‐based PLAU has the highest tensile modulus and elongation at break. They are all amorphous. The shape recovery of the three PLAUs is almost complete in a tensile elongation of 150% or a twofold compression. They can keep their temporary shape easily at room temperature (20 °C). More importantly, they can deform and recover at a temperature below their T_g values. Therefore, by selecting the appropriate hard segment and adjusting the ratio of hard to soft segments, they can meet different practical demands for shape memory medical devices. Copyright © 2007 Society of Chemical Industry     

Synthesis,characterization and thermal dissociation of 2‐butoxyethanol‐blocked diisocyanates and their use in the synthesis of isocyanate‐terminated prepolymers

A series of blocked diisocyanates has been synthesized from toluene diisocyante (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4′‐diphenylmethane diisocyanate (MDI) and 2‐butoxyethanol. The synthesis of blocked diisocyanate adducts was confirmed by Fourier transform infrared, ¹H NMR, electron impact mass spectrometry and nitrogen analysis. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and carbon dioxide evolution were used to determine the minimum de‐blocking temperatures. De‐blocking temperatures determined by these three techniques were found to be in the order DSC > TGA > CO₂ evolution. The effect of different metal catalysts on thermal de‐blocking reaction of the blocked diisocyanates was studied, using the carbon dioxide evolution method. It was found that iron(III) oxide has the maximum catalytic activity on de‐blocking. The solubility of the blocked diisocyanate adducts was determined in different solvents. The study revealed that at 30 °C blocked IPDI and HDI adducts show better solubility than adducts based on TDI and MDI. Isocyanate‐terminated prepolymers of blocked diisocyanates and hydroxyl‐terminated polybutadiene (HTPB) were prepared. The storage stability and gelation times of the prepolymers were studied. Results showed that all the diisocyanate‐HTPB compositions are stable at 50 °C for more than three months. However, aliphatic diisocyanate‐HTPB compositions require greater gelation time than aromatic diisocyanate‐HTPB compositions at their respective de‐blocking temperatures. Copyright © 2007 Society of Chemical Industry     

Thermal and mechanical properties of compression‐molded pMDI‐reinforced PCL/gluten composites

Many biopolymers and synthetic polymers composites were developed by different researchers for environmental protection and for cost reduction. One of these composites is polycaprolactone (PCL) and vital wheat gluten or wheat flour composites were prepared and compatibilized with polymeric diphenylmethane diisocyanate (pMDI) by blending and compression‐molding. PCL/pMDI blend exhibited glass transition (T_g) at ?67°C (0.20 J/g/°C) and vital gluten at 63°C (0.45 J/g/°C), whereas no T_g was recorded for wheat flour. Although T_g was unmistakable for either PCL or gluten, all composite exhibited one T_g, which is strong indication of interaction between PCL and the fillers. Several samples amongst the blended or compression‐molded composites exhibited no T_g signifying another confirmation of interaction. The ΔH of the endothermic (melting) and the exothermic (crystallization) for PCL was decreased as the percentage of gluten or flour increased, whereas the overall ΔH was higher for all composites compared to the theoretical value. The presence of pMDI appeared to strengthen the mechanical properties of the composites by mostly interacting with the filler (gluten or flour) and not as much with PCL. The FTIR analysis ruled out covalent interaction between PCL, pMDI, or the fillers but suggested the occurrence of physical interactions. Based on the data presented here and the data published earlier, the presence of pMDI did not change the nature of interaction between PCL and gluten, but it improved the mechanical properties of the composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyurethanes with monodisperse rigid segments based on a diamine–diamide chain extender

Polyether(bisurethane‐bisurea‐bisamide)s (PEUUA) based on poly(tetramethylene oxide) (PTMO) were synthesized by chain extension of PTMO endcapped with a diisocyanate (DI), and a diamine–diamide extender. The prepolymers were PTMOs with molecular weights between 1270 and 2200 g mol^?1, either endcapped with 4,4′‐diphenylmethane diisocyanate (MDI), 2,4‐toluene diisocyanate (2,4‐TDI), or 1,6‐hexane diisocyante (HDI) and with a low content of free diisocyanate (<0.1 wt %). The diamine–diamide (6A6) extender was based on hexamethylene diamine (6) and adipic acid (A). In this way, segmented polyurethanes with monodisperse rigid segments (DI‐6A6‐DI) were obtained. The PEUUAs were characterized by DSC as well as temperature‐dependent FTIR and DMTA. The mechanical properties of the polymers were evaluated by compression set and tensile test measurements. The polyurethanes with monodisperse rigid segments displayed low glass transition temperatures, almost temperature‐independent rubbery plateaus and sharp melting temperatures. The crystallinities of the hard segments were 70–80% upon heating and 40–60% upon cooling. The rate of crystallization was moderately fast as the supercooling (T_m ? T_c) was in the order 36–54°C. The polyurethanes based on HDI had a much higher rubber modulus as compared to the MDI and 2,4‐TDI‐based polymers, because of a higher degree of crystallinity and/or a higher aspect ratio of the crystallites. The HDI residues are flexible and not sterically hindered and could therefore be more easily packed than MDI or 2,4‐TDI residues. Polyurethanes with monodisperse DI‐6A6‐DI hard segments have interesting properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and properties of novel polyurethane insulating coatings based on glycerin‐terminated urethane prepolymers and blocked isocyanate

Novel polyurethane insulating coatings were prepared from the reaction of glycerin‐terminated polyurethane prepolymers (GPUPs) and a blocked isocyanate curing agent (BIC). The GPUPs were prepared from the reaction of one equivalent of polycaprolactone polyol (CAPA 210) with an excess amount of 4,4′‐methylene bis(phenyl isocyanate) (MDI) and subsequent reaction of the NCO‐terminated polyurethane with glycerin. The BIC was prepared from the reaction of trimethylol propane (TMP), toluene diisocyanate (TDI) and N‐methylaniline (NMA). The polyols and curing agent were characterized by conventional methods while the curing condition was optimized via gel content measurements. The curing kinetics of the polyurethane coating were investigated and the kinetic parameters derived. The crosslink densities of the samples were determined via the equilibrium swelling method, using the Flory–Rehner equation. The relationships between the crosslink density and the electrical, physical, mechanical and dynamic mechanical properties of the coatings were also studied. Copyright © 2005 Society of Chemical Industry     

Effect of the molecular structure of polyurethane elastomers on the thermomechanical properties of PUE/PC blends

Polyurethane elastomers (PUEs) based on 4,4′‐diphenylmethane diisocyanate (MDI), 1,4‐butanediol (BDO) and two kinds of aliphatic polycaprolactone (PCL) diols with molecular weight of 1000 Da and 2000 Da have been synthesized and melt‐blended with polycarbonate (PC). The compatibility of PC and PUEs was investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The results indicated that the glass transition temperature (T_g) of PC decreased by 0–40°C when 0–10 wt % of PUEs incorporated into the PC matrix. Phase separation in the blends was not detected by means of DSC characterization, but measurements of DMA and SEM indicated that phase separation existed in the blends of PC and PUEs synthesized with 1000 Da PCL‐diol. As for PUEs/PC blend in which 2000 Da PCL‐diol as PUEs' soft segments, it turned from completely compatible to partially when the NCO/OH ratio for the PUEs prepolymer was increased from 2 : 1 to 4 : 1. The compatibilities of PC and PUEs were greatly influenced by the molecular weight of polyols and the ratio of NCO/OH in the PUE prepolymer, higher molecular weight of polyols and lower NCO/OH ratio resulted in better compatibility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

In Situ synthesis of multiblock copolymers of poly(ϵ‐caprolactone) with different poly(ether diols) based polyurethane by reactive extrusion

Polyurethanes with multiblock copolymers of poly(?‐caprolactone) (PCL) and poly(tetramethylene oxide) glycol (PTMG) or poly(ethylene glycol) (PEG) as a soft segment were synthesized in situ via reactive extrusion from ?‐caprolactone (CL) and 4,4′‐diphenylmethane diisocyanate (MDI). The titanium alkoxide mixture generated from an ester‐exchange reaction between titanium propoxide [Ti(OPr)₄], and excessive PTMG or PEG was used as an initiator and catalyst. Compared to the reported fabrication of polycaprolactone‐based polyurethane (PCLU), the in situ reactive extrusion preparation not only explored a new rapid route for the fabrication of PCLU but also offered a simplified, controllable approach for the production of PCLU in a successive mass scale. A series of PTMG–PCLUs and PEG–PCLUs with different PCL block‐average degrees of polymerization (DP_n's) were prepared by only an adjustment of the relative concentration of CL in the reaction system, with a certain constant molar ratio of MDI to titanium alkoxide. ¹H‐NMR, gel permeation chromatography, and differential scanning calorimetry results indicate that all of the CL monomers were converted in the polymerization, and the molecular weight of the copolymers was about 8 × 10⁴ g/mol with a polydispersity index of approximate 2.4. With an increase in the PCL block‐average DP_n in PTMG–PCLU from 25 to 40, the tensile strength increased from 16.5 to 22.7 MPa, and the melting point increased from 46.1 to 49.5°C. It was also verified by PEG–PCLU prepared with organic Ti of lowered content in the initiator mixture that the mechanical properties could be greatly affected and dropped with decreasing content of organic Ti in the initiator mixture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Development of polyurethanes with azo‐type chromophores for second‐order nonlinear optical applications

Active nonlinear optical nitro‐substituted thiazole, benzothiazole, and thiadiazole chromophores were prepared and condensed with tolylene‐2,4‐diisocyanate (TDI) and 4,4′‐methylenedi(phenyl isocyanate) (MDI) to yield a series of polyurethanes. The resulting polyurethanes were characterized with Fourier transform infrared, proton nuclear magnetic resonance, and ultraviolet–visible spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The weight‐average molecular weights of the polyurethanes ranged between 19,500 and 28,000 (weight‐average molecular weight/number‐average molecular weight = 1.71–2.15). All the polyurethanes exhibited excellent solubility in most common organic solvents, and this indicated that these polyurethanes offered good processability. The glass‐transition temperatures (T_g's) of the polyurethanes were in the range of 166–204°C. Among the polyurethanes, chromophores containing the nitrothiazole moiety exhibited lower T_g values in comparison with those of chromophores containing nitrobenzothiazole and nitrothiadiazole moieties. This was attributed to the small size of the nitrothiazole moiety in the polyurethane matrix. The polyurethanes containing a TDI backbone demonstrated relatively high T_g values in comparison with those of the polyurethanes containing an MDI backbone. This was a result of an enhancement of the rigidity caused by the incorporation of a toluene ring into the polyurethane backbone. The second harmonic generation (SHG) coefficients of the poled polyurethane films ranged from 67.29 to 105.45 pm/V at 1064 nm. High thermal endurance of the poled dipoles was observed for all the polyurethanes. This was attributed to the formation of extensive hydrogen bonds between urethane linkages. Furthermore, none of the developed polyurethanes showed SHG decay below 150°C, and this signified their acceptability for nonlinear optical devices. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Reactive blends of gelatinized starch and polycaprolactone‐g‐glycidyl methacrylate

Blends of the modified polycaprolactone (PCL) and the gelatinized starch with glycerin were prepared. The modified PCL, PCL‐g‐glycidyl methacrylate (GPCL), was synthesized by melt reaction of PCL and glycidyl methacrylate (GMA) in the presence of benzoyl peroxide (BPO) in a Brabender mixer. The size of the dispersed starch in the GPCL matrix was found to be smaller than that in the PCL matrix. As the relative content of the GMA groups in the GPCL increases, the elongation at break of the blend showed the highest value at a grafted GMA content of 4.2 wt %. With the increase of the glycerin content in the starch, an abrupt change of the mechanical properties of the blend were observed between 40 and 50 wt % glycerin content based on the starch weight. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1507–1516, 2001     

Structure–property relationship of blocked diisocyanates: synthesis of polyimides using imidazole‐blocked isocyanates

Imidazole, 2‐methylimidazole and benzimidazole‐blocked aromatic and aliphatic diisocyanates have been prepared and polymerized with pyromellitic dianhydride in the presence of a basic catalyst. The polymers are characterized with FTIR, ¹H NMR and ¹³C NMR spectroscopy and GPC, DSC and TGA. The structure–property relationship of blocked diisocyanates are discussed in terms of molecular weight of the polyimides obtained. Considering the blocking agent, GPC results show that the benzimidazole blocked adduct yields higher molecular weight polymer than the 2‐methylimidazole‐blocked adduct which, in turn, yields higher molecular weight polymer than the imidazole‐blocked adduct. Considering the structure of the isocyanate, the molecular weight of polymer increases from isophorone diisocyanate to hexamethylene diisocyanate and to toluene diisocyanate (TDI). DSC traces of the polymers derived from TDI show glass transitions (T_g) in the temperature range 152–180 °C and the values increase from the polymer based on imidazole‐blocked TDI to 2‐methylimidazole‐blocked TDI and to benzimidazole‐blocked TDI. © 2000 Society of Chemical Industry     

Incorporation of azobenzene chromophore into poly(amide‐imide)

Poly(amide‐imide)s (PAI) bearing azobenzene chromophore groups were prepared by allowing a hydroxyl‐containing azobenzene dye (Disperse Red 1) to react with and reactive‐terminated PAI with weight–average molecular weights ranging from ～ 1.2 to 2.0 × 10⁴ g/mol. Such PAI were prepared by the condensation of trimellitic anhydride (TMA) and 4,4′‐methylene diphenyl diisocyanate (MDI). The final polymers presented a deep red color, with an absorption maxima in N,N‐dimethylformamide (DMF) solution at 490 nm, close to the azobenzene reactant used (Disperse Red 1) and molecular weights slightly higher than the pristine polymer, showing that the azo chromophore incorporation reaction does not lead to side reactions. The azofunctionalized polymer presented a high T_g value (170°C) that could be increased by a thermal curing process to 240°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 841–847, 2007     

Synthesis,characterization, and thermal degradation kinetic of polystyrene‐g‐polycaprolactone

In the present study, it has been demonstrated that polystyrene‐g‐polycaprolactone (PS‐g‐PCL) was successfully prepared by “click chemistry.” For this purpose, first, poly(styrene‐co‐4‐chloromethylstyrene) (P(S‐co‐CMS)) with 4‐chloromethylstyrene content (10%) was synthesized. Second, alkyne‐functionalized polycaprolactone (PCL) was obtained using propargyl alcohol and caprolactone. P(S‐co‐CMS) and PCL were reacted in N,N‐dimethylformamide for 24 h at 25°C to give PS‐g‐PCL. The synthesized polymer was characterized by nuclear magnetic resonance (¹H‐NMR), gel permeation chromatography, Fourier transform infrared spectroscopy and thermogravimetric analysis. The apparent activation energies for thermal degradation of PS‐g‐PCL were obtained by differential (Kissenger) and integral methods (Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Tang, Coats–Redfern, Van Krevelen et al.). The decomposition mechanism and pre‐exponential factor were calculated in terms of Coats–Redfern method. The most likely decomposition processes of first and second degradation stages were A_n type and F₃ type, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of annealing on poly(urethane‐siloxane) copolymers

Poly(urethane‐siloxane) copolymers were prepared by copolymerization of OH‐terminated polydimethylsiloxane (PDMS), which was utilized as the soft segment, as well as 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (1,4‐BD), which were both hard segments. These copolymers exhibited almost complete phase separation between soft and hard segments, giving rise to a very simple material structure in this investigation. The thermal behavior of the amorphous hard segment of the copolymer with 62.3% hard‐segment content was examined by differential scanning calorimetry (DSC). Both the T₁ temperature and the magnitude of the T₁ endotherm increased linearly with the logarithmic annealing time at an annealing temperature of 100°C. The typical enthalpy of relaxation was attributed to the physical aging of the amorphous hard segment. The T₁ endotherm shifted to high temperature until it merged with the T₂ endotherm as the annealing temperature increased. Following annealing at 170°C for various periods, the DSC curves presented two endothermic regions. The first endotherm assigned as T₂ was the result of the enthalpy relaxation of the hard segment. The second endothermic peak (T₃) was caused by the hard‐segment crystal. The exothermic curves at an annealing temperature of above 150°C exhibited an exotherm caused by the T₃ microcrystalline growth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5174–5183, 2006     

Crosslinking reaction and properties of two‐component waterborne polyurethane from terpene‐maleic ester type epoxy resin

A two‐component waterborne polyurethane (2K‐WPU) is prepared with the terpene‐maleic ester type epoxy resin‐based polyol dispersion and a hydrophilically modified hexamethylene diisocyanate tripolymer. Laser particle size analyzer and transmission electron microscopy are used to characterize the particle size distribution and the micromorphology of the 2K‐WPU. Crosslinking reaction kinetics of the 2K‐WPU is examined by fourier transform infrared spectrometry (FTIR) spectra. In the preliminary stage of the crosslinking reaction, it shows a very good fit with a second order reaction kinetics, and the apparent activation energy is 94.61 kJ mol^?1. It is also shown from the FTIR spectra that the complete crosslinking reaction of the 2K‐WPU needs 7 h at 70°C. The crosslinked products of the 2K‐WPU have good thermal resistant properties, with glass‐transition temperatures (T_g) in the range of 35–40°C and 10% weight loss temperatures (T_d) in the range of 275–287°C. The films obtained from the crosslinked products have good water‐resistance, antifouling, blocking resistance properties and impact strength of >50 cm, flexibility of 0.5 mm, adhesion of 1 grade, pencil hardness of HB‐2H. The pencil hardness and thermal‐resistant properties of the crosslinked products increase with the molar ratio of isocyanate (? NCO) group to hydroxyl (? OH) group. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis functional poly(carbonate‐b‐ester) copolymers and micellar characterizations

Functional poly(carbonate‐b‐ester)s were synthesized in buck by ring‐opening polymerization of the carbonate (TMC, MBC, or BMC) with tert‐butyl N‐(2‐hydroxyethyl) carbamate as an initiator, and then with ε‐CL (or ε‐BCL) comonomer. Subsequently, the PMMC‐b‐PCL with pendent carboxyl groups and the PTMC‐b‐PHCL with pendent hydroxyl groups were obtained by catalytic debenzylation. DSC analysis indicated that only one T_g at an intermediate temperature the T_gs of the two polymer blocks. A decrease T_g was observed when an increase contents of ε‐CL incorporated into the copolymers. In contrast, two increased T_ms were observed with increasing PCL content. The block copolymers formed micelle in aqueous phase with critical micelle concentrations (cmcs) in the range of 2.23–14.6 mg/L and with the mean hydrodynamic diameters in the range of 100–280 nm, depending on the composition of copolymers. The drug entrapment efficiency and hydrolytic degradation behavior of micelle were also evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Characterization of biodegradable polymers by inverse gas chromatography. II. Blends of amylopectin and poly(ε‐caprolactone)

Amylopectin (AP), a potato‐starch‐based polymer with a molecular weight of 6,000,000 g/mol, was blended with poly(ε‐caprolactone) (PCL) and characterized with inverse gas chromatography (IGC), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). Five different compositions of AP–PCL blends ranging from 0 to 100% AP were studied over a wide range of temperatures (80–260°C). Nineteen solutes (solvents) were injected onto five chromatographic columns containing the AP–PCL blends. These solutes probed the dispersive, dipole–dipole, and hydrogen‐bonding interactions, acid–base characteristics, wettability, and water uptake of the AP–PCL blends. Retention diagrams of these solutes in a temperature range of 80–260°C revealed two zones: crystalline and amorphous. The glass‐transition temperature (T_g) and melting temperature (T_m) of the blends were measured with these zones. The two zones were used to calculate the degree of crystallinity of pure AP and its blends below T_m, which ranged from 85% at 104°C to 0% at T_m. IGC complemented the DSC method for obtaining the T_g and T_m values of the pure AP and AP–PCL blends. These values were unexpectedly elevated for the blends over that of pure AP and ranged from 105 to 152°C for T_g and from 166 to 210°C for T_m. The T_m values agreed well with the XRD analysis data. This elevation in the T_g and T_m values may have been due to the change in the heat capacity at T_g and the dependence of T_g on various variables, including the molecular weight and the blend composition. Polymer blend/solvent interaction parameters were measured with a variety of solutes over a wide range of temperatures and determined the solubility of the blends in the solutes. We were also able to determine the blend compatibility over a wide range of temperatures and weight fractions. The polymer–polymer interaction coefficient and interaction energy parameter agreed well on the partial miscibility of the two polymers. The dispersive component of the surface energy of the AP–PCL blends was measured with alkanes and ranged from 16.09 mJ/m² for pure AP to 38.26 mJ/m² when AP was mixed with PCL in a 50/50% ratio. This revealed an increase in the surface energy of AP when PCL was added. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3076–3089, 2006     

Synthesis and characterization of biodegradable poly(ester‐urethanes) based on bacterial poly(R‐3‐hydroxybutyrate)

A series of poly(R‐3‐hydroxybutyrate)/poly(ε‐caprolactone)/1,6‐hexamethylene diisocyanate‐segmented poly(ester‐urethanes), having different compositions and different block lengths, were synthesized by one‐step solution polymerization. The molecular weight of poly(R‐3‐hydroxybutyrate)‐diol, PHB‐diol, hard segments was in the range of 2100–4400 and poly(ε‐caprolactone)‐diol, PCL‐diol, soft segments in the range of 1080–5800. The materials obtained were investigated by using differential scanning calorimetry, wide angle X‐ray diffraction and mechanical measurements. All poly(ester‐urethanes) investigated were semicrystalline with T_m varying within 126–148°C. DSC results showed that T_g are shifted to higher temperature with increasing content of PHB hard segments and decreasing molecular weight of PCL soft segments. This indicates partial compatibility of the two phases. In poly(ester‐urethanes) made from PCL soft segments of molecular weight (M_n ≥ 2200), a PCL crystalline phase, in addition to the PHB crystalline phase, was observed. As for the mechanical tensile properties of poly(ester‐urethane) cast films, it was found that the ultimate strength and the elongation at the breakpoint decrease with increasing PHB hard segment content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 703–718, 2002     

PCL–PEG–PCL triblock ester–ether copolydiol-based waterborne polyurethane. II. Effect of NCO/OH mole ratio and DMPA content on the physical properties

This article was focused on the effects of the NCO/OH molar ratio and 2,2-bis(hydroxyl methyl) propionic acid (DMPA) content during prepolymerization on the physical properties of synthesized waterborne polyurethane (WBPU) by using the polycaprolactone–poly(ethyl glycol)–polycaprolactone triblock copolydiol (PCL–PEG–PCL) as the soft segment. The results showed that the particle size of the WBPUs' dispersion decreased with a decreasing NCO/OH molar ratio or increasing DMPA content. Regarding thermal and mechanical properties, the WBPUs had a higher T_g's and lower T_m's and a higher breaking stress and a lower breaking strain of film with the NCO/OH molar ratio or DMPA content increase. The increasing NCO/OH molar ratio was advantageous to the water vapor permeability (WVP)-breaking stress balance, but the effect of the DMPA content on the WVP was not significant. The WBPU with PCL–PEG–PCL as the soft segment had a smaller particle size in dispersion and a better WVP-breaking stress balance than those of WBPU with the blending PCL and PEG as the soft segment. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1301–1311, 1998