Novel poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers through atom transfer radical polymerization

Poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers have been synthesized successfully through atom transfer radical polymerization of methyl methacrylate using telechelic bromo‐terminated polyurethane/CuBr/N,N,N,N″,N″‐pentamethyldiethylenetriamine initiating system. As the time increases, the number‐average molecular weight increases linearly from 6400 to 37,000. This shows that the poly methyl methacrylate blocks were attached to polyurethane block. As the polymerization time increases, both conversion and molecular weight increased and the molecular weight increases linearly with increasing conversion. These results indicate that the formation of the tri‐block copolymers was through atom transfer radical polymerization mechanism. Proton nuclear magnetic resonance spectral results of the triblock copolymers show that the molar ratio between polyurethane and poly (methyl methacrylate) blocks is in the range of 1 : 16.3 to 1 : 449.4. Differential scanning calorimetry results show T_g of the soft segment at ?35°C and T_g of the hard segment at 75°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of novel polystyrene‐block‐polyurethane‐block‐polystyrene tri‐block copolymers through atom transfer radical polymerization

Background: Radical polymerization is used widely to polymerize more than 70% of vinyl monomers in industry, but the control over molecular weight and end group of the resulting polymers is always a challenging task with this method. To prepare polymers with desired molecular weight and end groups, many controlled radical polymerization (CRP) ideas have been proposed over the last decade. Atom transfer radical polymerization (ATRP) is one of the successful CRP techniques. Using ATRP, there is no report on the synthesis of polystyrene‐block‐polyurethane‐block‐polystyrene (PSt‐b‐PU‐b‐PSt) tri‐block copolymers. Hence this paper describes the method of synthesizing these tri‐block copolymers. To accomplish this, first telechelic bromo‐terminated polyurethane was synthesized and used further to synthesize PSt‐b‐PU‐b‐PSt tri‐block copolymers using CuBr as a catalyst and N,N,N,N″,N″‐pentamethyldiethylenetriamine as a complexing agent. Results: The ‘living’ nature of the initiating system was confirmed by linear increase of number‐average molecular weight and conversion with time. A semi‐logarithmic kinetics plot shows that the concentration of propagating radical is steady. The results from nuclear magnetic resonance spectroscopy, gel permeation chromatography and differential scanning calorimetry show that the novel PSt‐b‐PU‐b‐PSt tri‐block copolymers were formed through the ATRP mechanism. Conclusion: For the first time, PSt‐b‐PU‐b‐PSt tri‐block copolymers were synthesized through ATRP. The advantage of this method is that the controlled incorporation of polystyrene block in polyurethane can be achieved by simply changing the polymerization time. Copyright © 2007 Society of Chemical Industry     

Controlled radical polymerization of styrene initiated by diethyldithiocarbamate‐mediated iniferters

We demonstrated that density functional theory calculations provide a prediction of the trends in C‐S bond dissociation energies and atomic spin densities for radicals using two model compounds as diethyldithiocarbamate (DC)‐mediated iniferters. On the basis of this information, we synthesized 2‐(N,N‐diethyldithiocarbamyl)isobutylic acid (DTCA) and (4‐cyano‐4‐diethyldithiocarbamyl)pentanoic acid (CDPA) as DC‐mediated iniferters. Free‐radical polymerizations of styrene (St) were carried out in benzene initiated by DTCA or CDPA under UV irradiation. The first‐order time‐conversion plots showed the straight line for the UV irradiation system initiated by CDPA indicating the first order in monomer. The number‐average molecular weight (M_n) of the polystyrene (PSt) increased in direct proportion to monomer conversion. The molecular weight distribution (M_w/M_n) of the PSt was in the range of 1.3–1.7. It was concluded this polymerization system proceeded with a controlled radical mechanism. However, photopolymerization of styrene initiated by DTCA showed nonliving polymerization consistent with UV initiation. Theoretical predictions supported these experimental results. Methacrylic acid (MA) could also be polymerized in a living fashion with such a PSt precursor as a macroinitiator because PSt exhibited a DC group at its terminal end. This system could be applied to the architecture of block copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 413–418, 2005     

‘Living’ Radical Polymerization of Styrene Using Tetraphenylethane-based Polyurethane Iniferter

A novel polyurethane iniferter synthesized from 1,1,2,2-tetraphenyl-1,2-ethane diol and toluene diisocyanate has been used to polymerize styrene through a ‘living’ radical mechanism. A rate equation (R_p∝[styrene]^1·1 [polyurethane iniferter]^0·93) and overall activation energy (E_a=99kJmol^-1) have been deduced from the kinetic results. The molecular weight of the polystyrene increased with increasing polymerization time and conversion. When the polystyrene was post-polymerized in the presence of styrene and methyl methacrylate, a high molecular weight polystyrene and polystyrene–poly(methyl methacrylate) block copolymer were obtained, respectively. © 1997 SCI.     

Surface behavior and micelle morphology of novel nonionic polyurethane bolaform amphiphilic block copolymers

A novel series of nonionic bolaamphiphiles—polyurethane amphiphilic block copolymers were synthesized by addition polymerization. Their chemical structures were characterized using FTIR and ¹H-NMR spectra. The critical micelle concentration was determined by surface tensiometer and UV-vis absorption spectra. The surface behaviors of copolymers at air/water interface were also investigated including the effects of concentration, molecular structure, electrolytes, and rest time. The results show that these bolaform polyurethane amphiphilic block copolymers exhibited excellent surface activity: PU₃₄ could attain surface tension as low as 35.6 mN m⁻¹. According to the images of Transmission Electron Microscopy (TEM), the copolymers could self-assemble star-like aggregates comprised of hydrophobic block PPO surrounded by hydrophilic block PEO. Moreover, variation of concentration, the weight fraction of the hydrophilic block (f_phil), and the molecular weight of the copolymers could lead to the transformation of micelle (or premicelle) morphology. This provides a new and simple way to obtain nanoparticles with control over structure on the nanometer scale.     

Polyurethane tri‐block copolymers—Synthesis,mechanical, elastic,and rheological properties

A series of polyurethane tri‐block copolymers were synthesized by reacting a 4,4′‐methylenebis(phenyl isocyanate) (MDI)‐endcapped poly(tetramethylene oxide) (PTMO, M_n = 2,000 g/mol) with a monoamine‐diamide (6T6m) hard segment (HS). The concentration of the HS in the copolymer was varied between 9 and 33 wt % by changing the length of the soft mid‐block segment. The structure of the copolymers was analyzed by nuclear magnetic resonance, the amide crystallinity was investigated by Fourier transform infra‐red and the thermal properties were studied by differential scanning calorimetry. The mechanical and elastic properties of the tri‐block copolymer were subsequently explored by dynamic mechanical analysis, compression set and tensile experiments, and the melt rheological behavior was studied by a parallel plate method. The amide end groups displayed a high crystallinity and the modulus of the tri‐block copolymers was relatively high. The fracture strain increased strongly with the molecular weight and the copolymers demonstrated a ductile fracture behavior for molecular weights above 6000 g/mol. Good compression set values were obtained for the tri‐block copolymers despite their low molecular weight. In the molten state, the tri‐block polymers displayed a gelling effect at low frequencies, which was believed to be a result of a clustering of the end‐segments. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effect of molecular weight on spherulitic growth rate of poly(ϵ‐caprolactone) and poly(ϵ‐caprolactone)‐b‐poly(ethylene glycol)

The spherulitic growth rates of a series poly (?‐caprolactone) homopolymers and poly(?‐caprolactone)‐b‐ poly(ethylene glycol) (PCL‐b‐PEG) block copolymers with different molecular weights but narrow polydispersity were studied. The results show that for both PCL homopolymers and PCL‐b‐PEG block copolymers, the spherulitic growth rate first increases with molecular weight and reaches a maximum, then decreases as molecular weight increases. Crystallization temperature has greater influence on the spherulitic growth rate of polymers with higher molecular weight. Hoffman–Lauritzen theory was used to analyze spherulitic growth kinetics and the free energy of the folding surface (σ_e) was derived. It is found that the values of σ_e decrease with molecular weight at low molecular weight level and become constant for high molecular weight polymers. The chemically linked PEG block does not change the values of σ_e significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The kinetics of dithiocarbamate-mediated polyurethane-block-poly(methyl methacrylate) polymers

One important advantage offered by polymeric iniferters is the possibility that polycondensation polymers could be further reacted with vinyl monomers to produce novel block copolymers with interesting properties. The objective of this work was the kinetic investigation of polyurethane-block-poly(methyl methacrylate) (PU-b-PMMA) using dithiocarbamate (DC)-based polyurethane macroiniferter (PUMI) at different concentrations. It is shown that the copolymerization reactions followed the first order dependency. A linear increase of molecular weight with monomer conversion demonstrated that the copolymerization followed the mechanism of controlled radical polymerization. The rate of polymerization (R_p) at specific reaction time increased as the PUMI concentration increased from 0.34 × 10⁻³ mol/L to 2.74 × 10⁻³ mol/L, pass through a maxima, and decreased as PUMI concentration was increased beyond 2.74 × 10⁻³ mol/L. The thermogravimetric analysis showed that both PUMI and PU-b-PMMA degraded in three distinctive stages but the PU-b-PMMA is thermally more stable than the PUMI especially at lower temperatures. Thus, a combination of polycondensation and free radical photopolymerization methods, as demonstrated in this study, could be used to synthesize polyurethane-based block copolymers with tailored chain lengths of different blocks suitable for biomedical applications.     

Benzoin‐terminated polyurethane as macrophotoinitiator for synthesis of polyurethane–polymethyl methacrylate block copolymers

Macromolecular photoinitiators have attracted much attention in the recent years. They combine the properties of polymers with those of low‐molecular weight photoinitiators. These are polymers having side‐ or main‐chain photoreactive groups and can be used to make tailor‐made graft and block copolymers. Benzoin is an important photoinitiator, and polymers containing terminal photoactive benzoin group can initiate polymerization of vinylic monomers to give block copolymers. In the present case, we report the synthesis of polyurethane macrophotoinitiator with benzoin end group, which was subsequently used to synthesize polyurethane–polymethyl methacrylate block copolymers. The block copolymers were characterized by FTIR, ¹H NMR, TGA, scanning electron microscopic analysis, and solution viscometry studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(vinyl chloride)–polyol (AB)x block copolymers: Synthesis,characterization, and mechanical properties

Poly(vinyl chloride)–polyol (AB)_x block copolymers have been prepared by the condensation polymerization of low-molecular-weight hydroxy-terminated poly(vinyl chlorides) (PVC) and diisocyanate-capped polyester and polyether diols. The difunctional poly(vinyl chlorides) were synthesized by ozonization of commercial resin followed by metal hydride reduction. The (AB)_x block copolymers, which contained 3000 or 4300 molecular weight PVC block sizes and 1000–2000 molecular weight polyol segments, had a wide range of mechanical properties, depending on overall polymer structure. Tensile strengths ranged from 7.8 to 31.5 MPa, elongations from 125% to 610% and torsional stiffness temperatures (T_f) from 25°C to ?22°C.     

Synthesis and aggregation behavior of four types of different shaped PCL‐PEG block copolymers

Biodegradable, amphiphilic, linear (diblock and triblock) and star‐shaped (three‐armed and four‐armed) poly[(ethylene glycol)‐block‐(ε‐caprolactone)] copolymers (PEG–PCL copolymers) were synthesized by ring‐opening polymerization of ε‐caprolactone (CL) with stannous octoate as a catalyst, in the presence of monomethoxypoly(ethylene glycol) (MPEG), poly(ethylene glycol) (PEG), three‐armed poly(ethylene glycol) (3‐arm PEG) or four‐armed poly(ethylene glycol) (4‐arm PEG) as an initiator, respectively. The monomer‐to‐initiator ratio was varied to obtain copolymers with various PEG weight fractions in a range 66–86%. The molecular structure and crystallinity of the copolymers, and their aggregation behavior in the aqueous phase, were investigated by employing ¹H‐NMR spectroscopy, gel permeation chromatography and differential scanning calorimetry, as well as utilizing the observational data of gel–sol transitions and aggregates in aqueous solutions. The aggregates of the PEG–PCL block copolymers were prepared by directly dissolving them in water or by employing precipitation/solvent evaporation technique. The enthalpy of fusion (ΔH_m), enthalpy of crystallization (ΔH_crys) and degrees of crystallinity (χ_c) of PEG blocks in copolymers and the copolymer aggregates in aqueous solutions were influenced by their PEG weight fractions and molecular architecture. The gel–sol transition properties of the PEG–PCL block copolymers were related to their concentrations, composition and molecular architecture. Copyright © 2006 Society of Chemical Industry     

Synthesis and characterization of block copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The block copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,4-butanediol, and poly(tetramethylene ether) glycol (PTMEG) with molecular weights of 650, 1000, and 2000. The block copolymers were characterized by Fourier transform infrared and ¹H-NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), and X-ray diffraction. The block copolymer compositions were governed by the charge molar ratio (x) of PTMEG to dimethyl 2,6-naphthalenedicarboxylate. It was found that the thermal transitions were dependent on the compositions. As x increases, T_m and ΔH_m of the polyester segments decrease due to the decrease in the sequence length. The X-ray diffraction data also indicate that the crystallinity of the polyester segments decreased as x increased. The molecular weight of the PTMEG used has a significant influence on the glass transition temperature (T_g) and the crystallizability of the polyether segments. The polyether segments of block copolymers derived from PTMEG 2000 could crystallize after cooling and showed a T_g of about −67°C, independent of x. However, the polyether segments of copolymers derived from PTMEG 1000 and PTMEG 650 could not crystallize, and the T_g of the polyether segments decreased as x increased. This is described as the difference in the miscibility between amorphous parts of the polyether segments and those of the polyester segments. The TGA results indicate that the composition had little effect on the nonisothermal thermal degradation under nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1411–1418, 1997     

RAFT synthesis of poly(N‐isopropylacrylamide) and poly(methacrylic acid) homopolymers and block copolymers: Kinetics and characterization

Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used successfully to synthesize temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm), poly(methacrylic acid) (PMAA), and their temperature‐responsive block copolymers. Detailed RAFT polymerization kinetics of the homopolymers was studied. PNIPAAm and PMAA homopolymerization showed living characteristics that include a linear relationship between M _n and conversion, controlled molecular weights, and relatively narrow molecular weight distribution (PDI < 1.3). Furthermore, the homopolymers can be reactivated to produce block copolymers. The RAFT agent, carboxymethyl dithiobenzoate (CMDB), proved to control molecular weight and PDI. As the RAFT agent concentration increases, molecular weight and PDI decreased. However, CMDB showed evidence of having a relatively low chain transfer constant as well as degradation during polymerization. Solution of the block copolymers in phosphate buffered saline displayed temperature reversible characteristics at a lower critical solution temperature (LCST) transition of 31°C. A 5 wt % solution of the block copolymers form thermoreversible gels by a self‐assembly mechanism above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1191–1201, 2006     

Synthesis and characterization of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers with dibutylmagnesium as catalyst

Two series of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers were prepared by the ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) and dibutylmagnesium in 1,4‐dioxane solution at 70°C. The triblock structure and molecular weight of the copolymers were analyzed and confirmed by ¹H NMR, ¹³C NMR, FTIR, and gel permeation chromatography. The crystallization and thermal properties of the copolymers were investigated by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The results illustrated that the crystallization and melting behaviors of the copolymers were depended on the copolymer composition and the relative length of each block in copolymers. Crystallization exothermal peaks (T_c) and melting endothermic peaks (T_m) of PEG block were significantly influenced by the relative length of PCL blocks, due to the hindrance of the lateral PCL blocks. With increasing of the length of PCL blocks, the diffraction and the melting peak of PEG block disappeared gradually in the WAXD patterns and DSC curves, respectively. In contrast, the crystallization of PCL blocks was not suppressed by the middle PEG block. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of ABA‐type block copolymers of trimethylene carbonate and ϵ‐caprolactone

This paper describes the synthesis of a series of ABA‐type triblock copolymers of trimethylene carbonate and ?‐caprolactone with various molar ratios and analyses the thermal and mechanical properties of the resulting copolymers. The structures of the triblock copolymers were characterized by ¹H and ¹³C nuclear magnetic resonance spectroscopy, FT‐IR spectroscopy and gel permeation chromatography. Results obtained from the various characterization methods proves the successful synthesis of block copolymers of trimethylene carbonate and ?‐caprolactone. The thermal properties of the block copolymers were investigated by differential scanning calorimetry. The T_m and ΔH_m values of the copolymers decrease with increasing content of trimethylene carbonate units. Two T_gs were found in the copolymers. Furthermore, both of the T_g values increased with increasing content of trimethylene carbonate units. The mechanical properties of the resulting copolymers were studied by using a tensile tester. The results indicated that the mechanical properties of the block copolymers are related to the molar ratio of trimethylene carbonate and ?‐caprolactone in the copolymers, as well as the molecular weights of the resulting copolymers. The block copolymer with a molar composition of 50/50 possessed the highest tensile stress at maximum and modulus of elasticity. Block copolymers possessing different properties could be obtained by adjusting the copolymer compositions. Copyright © 2004 Society of Chemical Industry     

Self‐assembled structures in blends of disordered and lamellar block copolymers: SAXS,SANS and TEM study

BACKGROUND: The phase behaviour of copolymers and their blends is of great interest due to the phase transitions, self‐assembly and formation of ordered structures. Phenomena associated with the microdomain morphology of parent copolymers and phase behaviour in blends of deuterated block copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA), i.e. (dPS‐block‐dPMMA)₁/(dPS‐block‐PMMA)₂, were investigated using small‐angle X‐ray scattering, small‐angle neutron scattering and transmission electron microscopy as a function of molecular weight, concentration of added copolymers and temperature. RESULTS: Binary blends of the diblock copolymers having different molecular weights and different original micromorphology (one copolymer was in a disordered state and the others were of lamellar phase) were prepared by a solution‐cast process. The blends were found to be completely miscible on the molecular level at all compositions, if their molecular weight ratio was smaller than about 5. The domain spacing D of the blends can be scaled with M_n by D ～ M_n^2/3 as predicted by a previously published postulate (originally suggested and proved for blends of lamellar polystyrene‐block‐polyisoprene copolymers). CONCLUSIONS: The criterion for forming a single‐domain morphology (molecularly mixed blend) taking into account the different solubilization of copolymer blocks has been applied to explain the changes in microdomain morphology during the self‐assembling process in two copolymer blends. Evidently the criterion, suggested originally for blends of lamellar polystyrene‐block‐polyisoprene copolymers, can be employed to a much broader range of block copolymer blends. Copyright © 2008 Society of Chemical Industry     

Compatibilization effects of styrenic/rubber block copolymers in polypropylene/polystyrene blends

Compatibilizing effects of styrene/rubber block copolymers poly(styrene‐b‐butadiene‐b‐styrene) (SBS), poly(styrene‐b‐ethylene‐co‐propylene) (SEP), and two types of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS), which differ in their molecular weights on morphology and selected mechanical properties of immiscible polypropylene/polystyrene (PP/PS) 70/30 blend were investigated. Three different concentrations of styrene/rubber block copolymers were used (2.5, 5, and 10 wt %). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the phase morphology of blends. The SEM analysis revealed that the size of the dispersed particles decreases as the content of the compatibilizer increases. Reduction of the dispersed particles sizes of blends compatibilized with SEP, SBS, and low‐molecular weight SEBS agrees well with the theoretical predictions based on interaction energy densities determined by the binary interaction model of Paul and Barlow. The SEM analysis confirmed improved interfacial adhesion between matrix and dispersed phase. The TEM micrographs showed that SBS, SEP, and low‐molecular weight SEBS enveloped and joined pure PS particles into complex dispersed aggregates. Bimodal particle size distribution was observed in the case of SEP and low‐molecular weight SEBS addition. Notched impact strength (a_k), elongation at yield (ε_y), and Young's modulus (E) were measured as a function of weight percent of different types of styrene/rubber block copolymers. The a_k and ε_y were improved whereas E gradually decreased with increasing amount of the compatibilizer. The a_k was improved significantly by the addition of SEP. It was found that the compatibilizing efficiency of block copolymer used is strongly dependent on the chemical structure of rubber block, molecular weight of block copolymer molecule, and its concentration. The SEP diblock copolymer proved to be a superior compatibilizer over SBS and SEBS triblock copolymers. Low‐molecular weight SEBS appeared to be a more efficient compatibilizer in PP/PS blend than high‐molecular weight SEBS. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 291–307, 1999     

Synthesis of cyclohexanone formaldehyde resin‐methylmethacrylate block‐graft copolymers via ATRP

Well defined block‐graft copolymers of cyclohexanone‐formaldehyde resin (CFR) and methylmethacrylate (MMA) were prepared via atom transfer radical polymerization (ATRP). In the first step, cyclohexanone formaldehyde resin (CFR) containing hydroxyl groups were modified with 2‐bromopropionyl bromide. Resulting multifunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr) and N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (¹H‐NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular weight measurement. Molecular weight distributions of the CFR graft copolymers were measured by gel permeation chromatography (GPC). M_n values up to 19,000 associated with narrow molecular weight distributions (polydispersity index (PDI) < 1.6) were obtained with conversions up to 49%. Coating properties of synthesized graft copolymers such as adhesion and gloss values were measured. They exhibited good adhesion properties on Plexiglas substrate. The thermal behaviors of all polymers were conducted using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Synthesis of polyurethane–imide (PU–imide) copolymers with different dianhydrides and their properties

This study reports the synthesis of polyurethane–imide (PU–imide) copolymers using 4,4′-diphenylmethane diisocyanate (MDI) polytetramethylene glycols (PTMGs) and different aromatic dianhydrides. Differential scanning calorimetry (DSC) results indicate that PU–imide copolymers had two phase structures containing four transition temperatures (T_gs, T_ms, T_gh and T_mh). However, only PU–imide copolymers were formed by soft PTMG(2000) segments possessing a T_ms (melting point of soft segment). When different aromatic dianhydrides were introduced into the backbone chain of the polyurethane, although the T_gs (glass transition temperature of the soft segment) of some of PU–imide copolymers did not change, the copolymers with long soft segments had low T_gs values. The T_gh (glass transition temperature of hard segment) values of PU–imide copolymers were higher than that of polyurethane (PU). In addition, the high hard segment content of PU–imide copolymer series also had an obvious T_mh (melting point of hard segment). According to thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), the PU–imide copolymers had at least two stages of degradation. Although the T_di (initial temperature of degradation) depended on the hard segment content and the composition of hard segment, the different soft segment lengths did not obviously influence the T_di. However, PU–imide copolymers with a longer soft segment had a higher thermal stability in the degradation temperature range of middle weight loss (about T_d 5%–50%). However, beyond T_d 50% (50% weight loss at temperature of degradation), the temperature of degradation of PU–imide copolymers increased with increasing hard segment content. Mechanical properties revealed that the modulus and tensile strength of PU–imide copolymers surpassed those of PU. Wide angle X-ray diffraction patterns demonstrated that PU–imide copolymers are crystallizable. © 1999 Society of Chemical Industry