The effect of the soft segment of prepolymers on properties of poly(urethane‐ester) and its biodegradability

The influence of soft‐segment prepolymers prepared through the polymerization of δ‐valerolactone (VL) and 2,2‐dimethyl‐1,3‐propandiol (DP) monomers on the structure and properties of poly(urethane‐ester) as well as its biodegradability were investigated. Poly(urethane‐ester) was prepared in two steps. The first step was the preparation of prepolymers with various chain lengths by polymerizing VL and DP monomers in the presence of a distannoxane catalyst at 100 °C under nitrogen atmosphere. The second step was the preparation of poly(urethane‐ester) by polymerizing 4,4′‐methylene‐bis(phenyl isocyanate) (MDI) and prepolymers with various chain lengths in the absence of catalysts. The poly(urethane‐ester) was characterized through an analysis of functional groups (FTIR), thermal properties (differential thermal analysis/TGA), mechanical properties (tensile tester), crystallinity (XRD) and biodegradability. An increased chain length of the prepolymer used in polymerization with MDI leads to an increase in the thermal properties and crystallinity of poly(urethane‐ester). However, the maximum biodegradability in the activated sludge was observed in the poly(urethane‐ester) prepared by polymerizing MDI and prepolymers with a molar VL/DP ratio of 20/1. The amorphous parts of polymers were more easily decomposed by microorganism enzymes than were the crystalline parts after an incubation period of 30 days. Copyright © 2011 Society of Chemical Industry     

Synthesis and characterization of poly(urethane‐ester)s based on calcium salt of mono(hydroxybutyl)phthalate

Calcium‐containing poly(urethane‐ester)s (PUEs) were prepared by reacting diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and hydroxyl‐terminated poly(1,4‐butylene glutarate) [HTPBG₁₀₀₀], using di‐n‐butyltin‐dilaurate as catalyst. About six calcium‐containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:HTPBG₁₀₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4, and 1:3:4. Two blank PUEs were synthesized by the reaction of HTPBG₁₀₀₀ with diisocyanate (HMDI or TDI). The polymers were characterized by IR, ¹H NMR, Solid state ¹³C‐CP‐MAS NMR, TGA, DSC, XRD, solubility, and viscosity studies. The T_g value of PUEs increases with increase in the calcium content and decreases with increase in soft segment content. The viscosity of the calcium‐containing PUEs increases with increase in the soft segment content and decreases with increase in the 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 with increase in the calcium content of polymer, modulus (g′ and g″) increases at any given temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1720–1727, 2006     

Synthesis and thermal properties of poly(urethane‐imide)

The synthesis and thermal properties of thermoplastic poly(urethane‐imide) (PUI) resins were studied. Model reaction studies on the reactions of 4,4′‐diphenylcarbamatodiphenylmethane and 4,4′‐diisocyanatodiphenylmethane with phthalic anhydride were performed. We found that the reaction of anhydrides with urethane groups could take place under certain reaction conditions. According to the model reaction studies, N‐2‐methyl‐pyrrolidone was employed as a solvent, and no catalyst was used in the polymerization. To restrain the side reaction of anhydrides with urethane groups, we adopted a two‐step chain‐extending procedure in a chain‐extending reaction. The inherent viscosity of PUI was 0.83–0.99 dL/g. The prepared polymers not only exhibited improved solubility in organic solvents but also formed flexible films. Thermogravimetric analysis showed that PUI exhibited a two‐step thermal weight‐loss pattern. The first step of the thermal degradation of PUI was attributed to the thermooxidizing cleavage of weak and labile linkage, such as urethane groups, isopropylidene, and methylene, except for imide rings. The polymer inherent viscosity decreased sharply during the first step of thermal degradation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 773–781, 2001     

Synthesis and characterization of new functional poly(urethane‐imide) crosslinked networks

To synthesize new functional poly(urethane‐imide) crosslinked networks, soluble polyimide from 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′‐oxydianiline, and maleic anhydride and polyurethane prepolymer from polycaprolactone diol, tolylene 2,4‐diisocyanate and hydroxyl ethyl acrylate were prepared. Poly(urethane‐imide) thin films were finally prepared by the reaction between maleimide end‐capped soluble polyimide (PI) and acrylate end‐capped polyurethane (PU). The effect of polyurethane content on dielectric constant, residual stress, morphology, thermal property, and mechanical property was studied by FTIR, prism coupler, Thin Film Stress Analyzer (TFSA), XRD, TGA, DMTA, and Nano‐indentation. Dielectric constant of poly(urethane‐imide) thin films (2.39–2.45) was lower than that of pure polyimide (2.46). Especially, poly(urethane‐imide) thin films with 50% of PU showed lower dielectric constant than other poly(urethane‐imide) thin films did. Lower residual stress and slope in cooling curve were achieved in higher PU content. Compared to typical polyurethane, poly(urethane‐imide) thin films exhibited better thermal stability due to the presence of the imide groups. The glass transition temperature, modulus, and hardness decreased with increase in the flexible PU content even though elongation and thermal expansion coefficient increased. Finally, poly(urethane‐imide) thin films with low residual stress and dielectric constant, which are strongly affected by the morphological structure, chain mobility, and modulus, can be suggested to apply for electronic devices by variation of PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 113–123, 2006     

The effect of processing routes on the thermal and mechanical properties of poly(urethane‐isocyanurate) nanocomposites

A systematic investigation of four processing routes was implemented so as to evaluate the thermal and mechanical properties of nanosilica (NS) reinforced poly(urethane‐isocyanurate) nanocomposites (NC). The NS dispersion in the Polmix and the Isomix routes was performed in the polyol and the isocyanate precursor, respectively. The Isopol and the Solvmix routes consisted on the dispersion of the filler after the mixing of the precursors and with the aid of solvents, respectively. The NS dispersion, fractography (SEM, TEM), flexural and tensile mechanical properties, thermogravimetric analysis and FTIR analysis of NCs was performed as a function of processing route, isocyanate index, and NS concentration. Each route produced a NC with distinct properties, which were correlated to the NS agglomeration degree and how the NS affected the thermal transitions of the HS and the relative ratio of urethane and isocyanurate chemical groups. For example, the NC prepared with the Polmix route had substantial improvements of σ_t and ε_t of around +40 and +52%, respectively and an improved thermal resistance of the Hard Segments. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42750.     

Compatibility,crystallinity and mechanical properties of poly(lactic acid)‐poly(ether‐block‐amide) based copper nanocomposites

Binary and ternary composites of poly(lactic acid) (PLA), poly(ether‐block‐amide) (PEBAX) and copper nanoparticles were prepared by melt blending in an internal mixer. Compatibility and molecular interactions between the three components of the nanocomposites were evaluated using scanning electron microscopy and Fourier transform infrared spectroscopy. It was found that the carbonyl groups of the PLA and copper nanoparticles interact. Also, PLA and PEBAX are compatible and develop molecular interactions between the C=O of PLA and the C=O and NH of PEBAX, forming dipole–dipole bonds and hydrogen bonds. The compatibility and molecular interaction between PLA and PEBAX are reduced by copper nanoparticles. The reduction of compatibility between PLA and PEBAX produced a lower storage modulus and lower strain at break in the ternary systems than in the blend PLA‐PEBAX. Copper nanoparticles enhanced the crystallinity of PLA. PLA responded more strongly to the nucleating effect of copper when PEBAX was added indicating a synergistic effect. The strain at break of PLA was enhanced by the addition of PEBAX but was severely reduced by the presence of nanoparticles. © 2020 Society of Chemical Industry     

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     

Synthesis and characterization of a poly(ether–ester) copolymer from poly(2,6 dimethyl‐1,4‐phenylene oxide) and poly(ethylene terephthalate)

A series of poly(ether–ester) copolymers were synthesized from poly(2,6 dimethyl‐1,4‐phenylene oxide) (PPO) and poly(ethylene terephthalate) (PET). The synthesis was carried out by two‐step solution polymerization process. PET oligomers were synthesized via glycolysis and subsequently used in the copolymerization reaction. FTIR spectroscopy analysis shows the coexistence of spectral contributions of PPO and PET on the spectra of their ether–ester copolymers. The composition of the poly(ether–ester)s was calculated via ¹H NMR spectroscopy. A single glass transition temperature was detected for all synthesized poly(ether–ester)s. T_g behavior as a function of poly(ether–ester) composition is well represented by the Gordon‐Taylor equation. The molar masses of the copolymers synthesized were calculated by viscosimetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Hydrolytic resistance of model poly(ether urethane ureas) and poly(ester urethane ureas)

Poly(ester urethane ureas) (PesURUs) and poly(ether urethane ureas) (PetURUs) synthesized from diphenylmethane-4,4′-diisocyanate and poly(butylene adipate) diol, and poly(tetramethylene oxide) diol or poly(propylene oxide) diol, respectively, were hydrolyzed at 70°C for various periods up to 16 weeks. Differences in thermal and mechanical properties of as-received dry samples are correlated with the number and strength of hydrogen bonds formed between urea/urethane groups of hard segments and polyester or polyether groups of soft segments. Gel permeation chromatography measurements show that the molar mass of linear PesURUs markedly decreases with the hydrolysis time, whereas that of linear PetURUs remains almost unaffected. PesURU crosslinked by polymeric isocyanate has lower crystallinity, but shows somewhat better resistance to hydrolysis than its linear counterpart because of its more stable three-dimensional molecular structure. Water uptake at 37°C, dynamic mechanical thermal analysis, and differential scanning calorimetry thermograms determined for redried hydrolyzed specimens concurrently show that advancing hydrolysis accounts for decrease in the crystallinity (if any) of soft polyester segments, in the efficacy of hydrogen bonding and in crosslinking density. Experimental data indicate that hydrolytic resistance of PetURUs is primarily determined by (1) the hydrolytic stability of individual types of present groups, (2) steric hindrances affecting the access of water molecules to these groups, and (3) the hydrophilicity of backbones. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 577–586, 1998     

Synthesis and characterization of isocyanic acid,m‐phenylenediiso‐propylidene based poly(urethane‐urea) dispersions containing different amount of 2,2‐Bis(hydroxyl methyl)propionic acid

Isocyanic acid, m‐phenylenediiso‐propylidene (m‐TMXDI)‐based anionic poly(urethane‐urea) dispersions were prepared by the prepolymer mixing process. The equivalent ratio of NCO/OH was kept constant at 1.8, while 2,2‐bis(hydroxyl methyl) propionic acid (DMPA) used was varied from 3 to 10 wt %. The colloidal stability of poly(urethane‐urea) dispersions arose entirely from the presence of ionized carboxylic acid groups. The chemical structure of poly(urethane‐urea) dispersions with various amount of DMPA were identified by FTIR and ¹³C NMR analysis. The test results showed that the hydrophilicity of poly(urethane‐urea) dispersions were increased with increase in DMPA content. The degree of chain extension was much lower than the values predicted theoretically due to the side reaction of a small amount of hydrophilic isocyanate‐terminated prepolymer with water. The average particle size of poly(urethane‐urea) dispersions were decreased with an increase in DMPA content, and this lead to an increase in viscosity. Also, the thermal degradation behavior were measured and was shown that the initial degradation temperature shifted to lower temperature with an increase in DMPA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5737–5746, 2006     

Synthesis,characterization, and pervaporation properties of segmented poly(urethane‐urea)s

Poly(urethane‐urea)s (PUUs) from 2,4‐tolylene diisocyanate (2,4‐TDI), poly(oxytetramethylene)diols (PTMO) or poly(butylene adipate)diol (PBA), and various diamines were synthesized and characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and density measurements. Transport properties of the dense PUU‐based membranes were investigated in the pervaporation of benzene–cyclohexane mixtures. It was shown that the pervaporation characteristics of the prepared membranes depend on the structure and length of the PUU segments. The PBA‐based PUUs exhibit good pervaporation performance along with a very good durability in separation of the azeotropic benzene–cyclohexane mixture. They are characterized by the flux value of 25.5 (kg μm m⁻² h⁻¹) and the separation factor of 5.8 at 25°C, which is a reasonable compromise between the both transport parameters. The PTMO‐based PUUs display high permeation flux and low selectivity in separation of the benzene‐rich mixtures. At the feed composition of 5% benzene in cyclohexane, their selectivity and flux are in the range of 3.2 to 11.7 and 0.4 to 40.3, respectively, depending on the length of the hard and soft segments. The chemical constitution of the hard segments resulting from the chain extender used does not affect the selectivity of the PUU membranes. It enables, however, the permeability of the membranes to be tailored. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1615–1625, 1999     

Synthesis and characterization of poly(o‐anisidine)/V2O5 and poly(o‐anthranilic acid)/V2O5 nanocomposites

Poly(o‐anisidine)/V₂O₅ and poly(o‐anthranilic acid)/V₂O₅ nanocomposites were prepared by in situ intercalative polymerization, and the structure and electrical properties of these nanocomposites were investigated using GPC, TGA, XRD, TEM, FTIR, UV‐vis as well as conductivity measurement. The results show that the steric effect and nature of the substituting groups in the aromatic ring has an influence on the structure and electrical properties of the nanocomposites. Poly(o‐anisidine) or poly(o‐anthranilic acid) exists as a monolayer of outstretched chains in the gallery of the V₂O₅ xerogel owing to the confined environment in the nanometer‐size gallery. And intercalation of poly(o‐anisidine) or poly(o‐anthranilic acid) can improve the conductivity of V₂O₅ xerogel. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of hyperbranched poly(silyl ester)s

Hyperbranched poly(silyl ester)s were synthesized via the A₂ + B₄ route by the polycondensation reaction. The solid poly(silyl ester) was obtained by the reaction of di‐tert‐butyl adipate and 1,3‐tetramethyl‐1,3‐bis‐β(methyl‐dicholorosilyl)ethyl disiloxane. The oligomers with tert‐butyl terminal groups were obtained via the A₂ + B₂ route by the reaction of 1,5‐dichloro‐1,1,5,5‐tetramethyl‐3,3‐diphenyl‐trisi1oxane with excess amount of di‐tert‐butyl adipate. The viscous fluid and soft solid poly(silyl ester)s were obtained by the reaction of the oligomers as big monomers with 1,3‐tetramethyl‐1,3‐bis‐β(methyl‐dicholorosilyl)ethyl disiloxane. The polymers were characterized by ¹H NMR, IR, and UV spectroscopies, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The ¹H NMR and IR analysis proved the existence of the branched structures in the polymers. The glass transition temperatures (T_g's) of the viscous fluid and soft solid polymers were below room temperature. The T_g of the solid poly(silyl ester) was not found below room temperature but a temperature for the transition in the liquid crystalline phase was found at 42°C. Thermal decomposition of the soft solid and solid poly(silyl ester)s started at about 130°C and for the others it started at about 200°C. The obtained hyperbranched polymers did not decompose completely at 700°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3430–3436, 2006     

Miscibility,morphology and mechanical properties of rubber‐modified biodegradable poly(ester‐urethanes)

Biodegradable, lactic acid based amorphous poly(ester‐urethane)s (PEU) were modified with poly(L‐lactic acid‐co‐ϵ‐caprolactone‐urethane) elastomer (P[LA/CL]U) by melt blending. The phase separation of P(LA/CL)U elastomer with three different ϵ‐caprolactone (CL) compositions (CL content 30, 50, and 70 mol %) and the mechanical properties of the resulting impact‐modified linear and branched PEU were investigated. The amounts of P(LA/CL)U elastomer in the PEU blends were 10, 15, 20, and 30 wt %. Dynamic mechanical thermal analysis (DMTA) of the blends with P(LA50/CL50)U and P(LA30/CL70)U elastomers revealed separate glass transition temperatures for rubber and matrix, indicating phase separation. No phase separation was found for P(LA70/CL30)U elastomer. The effect of mixing rate and temperature during processing on composite properties was tested by blending P(LA30/CL70)U rubber with PEU under various processing conditions. Impact modification studies were also made with two P(LA30/CL70)U elastomers having different amounts of functional groups. The influence of end‐functionalization and cross‐linking on mechanical properties was investigated in blends containing PEU and 15 wt % of these elastomers. Scanning electron microscopy (SEM) showed the morphology to change dramatically with increase in the degree of cross‐linking in the rubber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1074–1084, 2000     

Synthesis and characterization of poly(acrylate amic acid) and its application as negative‐tone photosensitive polyimides

The dianhydride monomer 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride and two diamine monomers, 4,4′‐diamino‐3,3′‐biphenyldiol (HAB) and 2,4‐diaminophenol dihydrochloride (DAP), were used to synthesize a series of poly(hydroxyl amic acid). Further functionalization by grafting acrylate groups yields the corresponding poly(acrylate amic acid) that underwent a crosslinking reaction on exposure to UV‐light and was used as a negative‐tone photosensitive polyimide (PSPI). The analysis of chemical composition and molecular weight of these poly(amic acid)s determined by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography revealed that the molecular weight of the poly(hydroxyl amic acid) increased with the molar content of HAB in the feedstock, because HAB exhibited higher polymerization reactivity than DAP. Moreover, the degree of grafting acrylate groups onto poly(hydroxyl amic acid) was determined by ¹H‐NMR spectroscopy. The photoresist was formulated by adding 2‐benzyl‐2‐N,N‐dimethylamino‐1‐(4‐morpholinophenyl) butanone (IRG369) and isopropylthioxanthone as a photoinitiator, tetra(ethylene glycol) diacrylate as a crosslinker, and tribromomethyl phenyl sulfone as a photosensitizer. The PSPI precursor exhibited a photosensitivity of 200 mJ/cm² and a contrast of 1.78. A pattern with a resolution of 10 μm was observed in an optical micrograph after thermal imidization at 300°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Segmented poly(urethane‐urea) elastomers based on polycaprolactone: Structure and properties

A series of segmented poly(urethane‐urea) polymers have been synthesized varying the hard segments content, based on the combination of polycaprolactone diol and aliphatic diisocyanate (Bis(4‐isocyanatocyclohexyl)methane), using diamine (1,4‐Butylenediamine) as the chain extender. The microstructure and properties of the material highly depend on the hard segments content (from 14 to 40%). These PUUs with hard segment content above 23% have elastomeric behaviors that allow high recoverable deformation. The chemical structure and hydrogen bonding interactions were studied using FTIR and atomic force microscopy, which revealed phase separation that was also confirmed by DSC, dynamic‐mechanical, and dielectric spectroscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(ester sulfoimide) from dichlorocarbonylimide of disaccharindicarboxylic acid and aromatic diols

A new chlorocarbonylimide of disaccharindicarboxylic acid was synthesized by condensation of imides of saccharin‐6‐carboxylic acid with alkyl‐ and alkylaryl bishalogenides. Poly(ester sulfoimide), soluble in organic solvents, was synthesized by polycondensation of chlorocarbonylimide with bisphenol. DTA and TGA investigations have shown that poly(ester sulfoimide)s were stable at temperatures up to 300°C–345°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1687–1691, 2006     

Synthesis,characterization and properties of biodegradable poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyesters

BACKGROUND: To obtain a biodegradable thermoplastic elastomer, a series of poly(ester‐ether)s based on poly(butylene succinate) (PBS) and poly(propylene glycol) (PPG), with various mass fractions and molecular weights of PPG, were synthesized through melt polycondensation. RESULTS: The copolyesters were characterized using ¹H NMR, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, mechanical testing and enzymatic degradation. The results indicated that poly(ester‐ether)s with high molecular weights were successfully synthesized. The composition of the copolyesters agreed very well with the feed ratio. With increasing content of the soft PPG segment, the glass transition temperature decreased gradually while the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased. Mechanical testing demonstrated that the toughness of PBS was improved significantly. The elongation at break of the copolyesters was 2–5 times that of the original PBS. Most of the poly(ester‐ether) specimens were so flexible that they were not broken in Izod impact experiments. At the same time, the enzymatic degradation rate of PBS was enhanced. Also, the difference in molecular weight of PPG led to properties being changed to some extent among the copolyesters. CONCLUSION: The synthesized poly(ester‐ether)s having excellent flexibility and biodegradability extend the application of PBS into the areas where biodegradable thermoplastic elastomers are needed. Copyright © 2009 Society of Chemical Industry     

Synthesis of biodegradable amino‐acid‐based poly(ester amide)s and poly(ether ester amide)s with pendant functional groups

A new family of biodegradable amino‐acid‐based poly(ester amide)s (AA–PEAs) and amino‐acid‐based poly(ether ester amide)s (AA–PEEAs) consisting of reactive pendant functional groups (? COOH or ? NH₂) were synthesized from unsaturated AA–PEAs and AA–PEEAs via a thiol–ene reaction in the presence of a radical initiator (2,2′‐azobisisobutyronitrile). The synthetic method was a one‐step reaction with near 100% yields under mild reaction conditions. The resulting functional AA–PEA and AA–PEEA polymers were characterized by Fourier transform infrared spectroscopy, NMR, and differential scanning calorimetry. These new functional AA–PEA and AA–PEEA derivatives had lower glass‐transition temperatures than the original unsaturated AA–PEA and AA–PEEA polymers, and their solubility in some organic solvents also improved. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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