Synthesis,characterization, and properties of two‐component amphiphilic polyoxyethylene–containing multiblock copolymers

Amphiphilic (oxyethylene–oxypropylene) and (oxyethylene–styrene) multiblock copolymers, both with high molecular weights, were synthesized by coupling poly(ethylene glycol) (PEG) with poly(propylene glycol) (PPG) or with telechelic dihydroxy polystyrene using 2,4‐toluene diisocyanate as a coupling agent, respectively. The polymerization conditions were investigated. The products were purified and characterized by IR, ¹H‐NMR spectroscopy, and membrane osmometry and identified as multiblock copolymers. Crystallinity of the two kinds of multiblock copolymers was determined by DSC. They showed good emulsifying properties. Their complexes with LiClO₄ showed high room‐temperature conductivities from 3 × 10⁻⁵ to 4 × 10⁻⁴ S/cm at 30°C. High molecular weight (oxyethylene–oxypropylene) multiblock copolymers, at a weight ratio of PEG/PPG = 6/4, behave like thermoplastic elastomers. The (oxyethylene–styrene) copolymer functions as a good compatibilizer for the blend of chlorohydrin rubber and polystyrene. An amount of only 3 wt %, based on the blend, is needed to increase the tensile strength of the blend almost sixfold. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1295–1301, 2005     

Synthesis and characterization of oxymethylene-linked 2-vinylpyridine/oxyethylene multiblock copolymers

Oxymethylene-linked (2-vinylpyridine-oxyethylene) multiblock copolymers were prepared by coupling telechelic α,ω-dihydroxypoly(2-vinylpyridine) (THPVP) and poly(ethylene oxide) (PEO), using dichloromethane as coupling agent and KOH as catalyst. THPVP was synthesized by polymerization of 2-vinylpyridine in tetrahydrofuran/benzene using 1-methylnaphthyllithium as anionic initiator, followed by capping with ethylene oxide and termination by methanol. The effects of charging weight ratio of PEO/THPVP, copolymerization time and molecular weight of PEO or THPVP on the copolymerization were studied. The copolymers were characterized by IR, ¹H NMR, membrane osmometry, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC).     

Behavior of poly(ethylene‐co‐olefin) polymers as elastomeric materials

The properties of two new ethylene‐α‐olefin copolymers, namely, ethylene–1‐hexene copolymer (EHC) and ethylene–1‐octadecene copolymers (EOC), synthesized via metallocene catalysts were evaluated. The copolymerization was carried out in an autoclave reactor with Et(Indenyl)₂ZrCl₂/methylaluminoxane as a catalyst system. These single‐site catalysts (metallocene type) allow one to obtain very homogeneous copolymers with excellent control of the molecular weight distribution and proportion of comonomer incorporation. So, copolymers with 18 mol % comonomer in the case of EHC and 12 mol % for EOC were shaped, and activities around 100,000 kg of polymer mol^?1 of Zr bar^?1 h^?1 were reached. The properties of these copolymers were compared with other commercial elastomers, such as ethylene–propylene copolymers synthesized by Ziegler–Natta catalysts and an ethylene–octene copolymer obtained via metallocene catalysts. The results show that these new copolymers, in particular, EOC, had excellent elastomeric properties. Furthermore, they had a relatively low viscosity, which implied a good response during processing. Moreover, the effectiveness of these copolymers as impact modifiers for polyolefins was also studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3008–3015, 2004     

Thermal and structural analysis of heparin–PEO–PDMS–PEO–heparin pentablock copolymers

ABCBA-type amphiphilic block copolymers comprising polydimethylsiloxane (PDMS), poly(ethylene oxide) (PEO), and heparin segments were synthesized by coupling reactions between end-functionalized oligomers. These multiblock copolymers were characterized to examine bulk properties using ¹H-NMR, FTIR, end-group analysis, and sulfur elemental analysis. Block copolymers were further characterized in bulk using differential scanning calorimetry and X-ray diffraction measurements. The PDMS glass transition remains unchanged with increasing PEO content, indicating coexistence of pure PDMS with mixed phases. Furthermore, endothermic melting of the block copolymers shifts to higher temperatures and becomes more intense with increasing PEO molecular weight. Additionally, the crystallinity of the PEO segment in the block copolymers increases with increasing PEO molecular weight. The PEO melting endotherm peak shifts from near 318 to 323 K with annealing. In the cooling thermogram, the block copolymers exhibit two crystallization exotherms, one near 303 K and the other near 193 K, attributed to PEO and PDMS recrystallization and nucleation, respectively. © 1994 John Wiley & Sons, Inc.     

Influence of racemization on stereocomplex‐induced gelation of water‐soluble polylactide–poly(ethylene glycol) block copolymers

Ring‐opening polymerization of L ‐ or D ‐lactide was realized at 140 °C for a period of 7 days in the presence of dihydroxyl poly(ethylene glycol) (PEG), with M?_n = 4000 g mol^?1, using zinc lactate as initiator. The resulting poly(L ‐lactide)–PEG–poly(L ‐lactide) and poly(D ‐lactide)–PEG–poly(D ‐lactide) triblock copolymers are water soluble with polylactide (PLA) block length ranging from 11 to 17 units. Both the tube inverting method and rheological measurements were used to evaluate the gelation properties of aqueous solutions containing single copolymers or L /D copolymer pairs. Stereocomplexation between poly(L ‐lactide) and poly(D ‐lactide) blocks is observed for mixed solutions. Hydrogel formation is detected in the case of relatively long PLA blocks (DP _PLA = 17), but not for copolymers with shorter PLA blocks (DP _PLA = 11–13) due to partial racemization of L ‐lactyl units. Racemization is largely reduced when the reaction time is shortened to 1 day. Under these conditions, DP _PLA of 8 is sufficient for the stereocomplexation of PLA–PEG block copolymers, and DP _PLA above 10 leads to the formation of hydrogels of PLA–PEG block copolymers. On the other hand, racemization appears as a general phenomenon in the (co)polymerization of L ‐lactide with Zn(Lac)₂ as initiator, although it is negligible or undetectable in the case of high molar mass polymers. Therefore, racemization is the limiting factor for the stereocomplexation‐induced gelation of water‐soluble PLA–PEG block copolymers where the PLA block length generally ranges from 10 to 30. Reaction conditions including initiator, time and temperature should be strictly controlled to minimize racemization. Copyright © 2010 Society of Chemical Industry     

Novel amphiphilic polymer gel electrolytes based on (PEG‐b‐GMA)‐co‐MMA

Amphiphilic conetwork–structured copolymers containing different lengths of ethylene oxide (EO) chains as ionophilic units and methyl methacrylate (MMA) chains as ionophobic units were prepared by free radical copolymerization and characterized by FTIR and thermal analysis. Polymer gel electrolytes based on the copolymers complexed with liquid lithium electrolytes (dimethyl carbonate (DMC) : diethyl carbonate (DEC) : ethylene carbonate (EC) = 1 : 1 : 1 (W/W/W), LiPF₆ 1.0M) were characterized by differential scanning calorimetry and impedance spectroscopy. A maximum ion conductivity of 4.27 × 10^?4 S/cm at 25^oC was found for the polymer electrolyte based on (PEG2000‐b‐GMA)‐co‐MMA with long EO groups. Moreover, the effect of temperature on conductivity of the amphiphilic polymer electrolytes obeys the Arrhenius equation. The good room temperature conductivity of the polymer electrolytes is proposed to relate to the enhancement in the amorphous domain of the copolymers due to their amphiphilic conetwork structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

TPA‐PPEs – New alternating donor copolymers for potential application in photovoltaic devices

A series of phenyleneethynylene copolymers with triphenylamine units as hole‐transporting moieties (TPA‐PPEs) were synthesized by the palladium‐catalyzed cross‐coupling polycondensation of diethynyltriphenylamines and selected dihalogen comonomers, for instance substituted benzene, thiophene, benzothiadiazole, or anthracene. Incorporation of the electron‐rich amino group into the PPE backbone does not interrupt the main chain conjugation. Furthermore, it has a decreasing effect on the oxidation potential, thus makes these polymers interesting as hole‐injection/hole‐transporting materials. The chemical structure of the new alternating copolymers was confirmed by ¹H and ¹³C NMR spectroscopy and elemental analysis and gel‐permeation chromatography (GPC; THF, M_n ≈ 15,000–30,000 g/mol) was conducted. Furthermore, their optical properties were investigated by UV/vis spectroscopy. The TPA‐PPEs exhibit absorption maxima at around 400 nm (π‐π*), except anthracene containing copolymer 3f (λ_max = 514 nm in THF) and benzothiadiazole containing one 3g (λ_max = 503 nm in THF). The TPA copolymers have oxidation potentials about 1.1 V (Ag/AgCl). They are good photoconducting materials ( 3a : I_Photo = 4 × 10^?10 A at 425 nm (400 V), 3g : I_Photo = 1.3 × 10^?11 A at λ_max = 500 nm (20 V)) and show emission after excitation at around 450 nm (560 nm 3f ). Their application in nonoptimized polymer solar cells (bulk heterojunction) led to power conversion efficiencies of around 1–1.8% after illumination with 100 mW/cm² of AM1.5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dielectric properties of lithium‐perchlorate‐filled acrylonitrile–hexyl methacrylate copolymer films

A series of poly(acrylonitrile‐co‐hexyl methacrylate), PAN‐co‐PHMA, copolymers with various hexyl methacrylate (HMA) contents were synthesized by emulsion technique. The incorporation of HMA units into the copolymers was confirmed by Fourier transform infrared and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Glass transition temperatures (T _g) and thermal decomposition temperatures of copolymers were determined by differential scanning calorimetry and thermogravimetric analysis. The T _g of copolymers were lowered monotonically by increasing HMA content, while thermal stabilities of copolymers were enhanced. The frequency dependence of dielectric properties of three different amounts of LiClO₄ salt doped copolymer films was investigated. The influence of molar fraction of HMA on dielectric constant and ac‐conductivity of copolymer films was examined. Samples with higher HMA contents showed better stability and conductivity, as a result of increase in free volume and the mobility of the dipoles. The ac conductivity of copolymers was also improved by increasing LiClO₄ salt which was due to the existence of more charge carriers. PAN(88)‐co‐PHMA(12) copolymer with 1.5 mol% of lithium salt exhibited ionic conductivity of the 7.8 × 10⁻⁴ S/cm at 298 K. POLYM. COMPOS., 38:1792–1799, 2017. © 2015 Society of Plastics Engineers     

Synthesis of and photodegradation in a series of poly(ethylene terephthalate)–co–4,4′-sulfonyldibenzoate yarns

Phototendering studies of poly(ethylene terephthalate) homopolymer yarn and a series of poly(ethylene terephthalate–co–4, 4′-sulfonyldibenzoate) copolymer yarns have shown that photosensitized degradation occurs more readily in the copolymers than in the homopolymer. A photo-oxidative mechanism involving the second monomer, dibutyl 4, 4′-sulfonyldibenzoate, has been proposed to account for the photosensitization. The photophysical processes in the second monomer, dibutyl 4, 4′-sulfonyldibenzoate, were studied by absorption and luminescence techniques. The lowest excited singlet and triplet in this compound were identified as the ¹(π, π^*) and ₃(π, π^*) states, respectively. The energy levels in the second monomer have been assigned as follows: ¹S₁ ～ 33,000 cm^?1, ¹S₂ ～ 42,000 cm^?1, and ³T₁ ～ 26,000 cm^?1.     

Preparation and characterization of polystyrene–poly(ethylene oxide) amphiphilic block copolymers via atom transfer radical polymerization: Potential application as paper coating materials

Poly(ethylene oxide) (PEO) monochloro macroinitiators or PEO telechelic macroinitiators (Cl‐PEO‐Cl) were prepared from monohydroxyfunctional or dihydroxyfunctional PEO and 2‐chloro propionyl chloride. These macroinitiators were applied to the atom transfer radical polymerization of styrene (S). The polymerization was carried out in bulk at 140°C and catalyzed by Copper(I) chloride (CuCl) in the presence of 2,2′‐bipyridine (bipy) ligand (CuCl/bipy). The amphiphilic copolymers were either A‐B diblock or A‐B‐A triblock type, where A block is polystyrene (PS) and B block is PEO. The living nature of the polymerizations leads to block copolymers with narrow molecular weight distribution (1.072 < M_w/M_n < 1.392) for most of the macroinitiators synthesized. The macroinitiator itself and the corresponding block copolymers were characterized by FTIR, ¹H NMR, and SEC analysis. By adjusting the content of the PEO blocks it was possible to prepare water‐soluble/dispersible block copolymers. The obtained block copolymers were used to control paper surface characteristics by surface treatment with small amount of chemicals. The printability of the treated paper was evaluated with polarity factors, liquid absorption measurements, and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. From our study, it is observed that the chain length of the hydrophilic block and the amount of hydrophobic block play an important role in modification of the paper surface. Among all of block copolymers synthesized, the PS‐b‐PEO‐b‐PS containing 10 wt % PS was found to retard water absorption considerably. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4304–4313, 2006     

Synthesis and properties of novel biodegradable triblock copolymers of poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one) and poly(ethylene glycol)

Novel biodegradable triblock copolymers of poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one) (PMMTC) with poly(ethylene glycol) (PEG), PMMTC-b-PEG-b-PMMTC, were synthesized by the ring-opening polymerization of MMTC in bulk, using the dihydroxyl PEG as initiator and Sn(Oct)₂ as catalyst. The triblock copolymers with different compositions were characterized by IR and ¹H NMR, their molecular weight was measured by gel permeation chromatography (GPC). The results showed that the molecular weight of triblock copolymers increased either with the increase of the molar ratio of MMTC in feed while the PEG chain length kept constant, or by lengthening the backbone chain of PEG block with the same ratio of MMTC in feed. The hydrophilicity of copolymers was greatly improved by incorporation of PEG block into polycarbonate. The in vitro hydrolytic/enzymatic degradation and controlled drug release properties of the triblock copolymers were also investigated.     

Solid polymer electrolytes based on nanocomposites of ethylene oxide–epichlorohydrin copolymers and cellulose whiskers

With the aim of developing ion‐conducting solid polymer electrolytes that combine high ionic conductivity with good mechanical properties, we prepared and investigated nanocomposites of LiClO₄‐doped ethylene oxide‐epichlorohydrin (EO‐EPI) copolymers and nanoscale cellulose whiskers derived from tunicates. We show that homogeneous nanocomposite films based on EO‐EPI copolymers, LiClO₄, and tunicate whiskers can be produced by solution‐casting THF/water mixtures comprising these components and subsequent compression‐molding. The Young's moduli of the nanocomposites thus produced are increased by a factor of up to >50, when compared to the copolymers, whereas the electrical conductivities experience only comparably small reductions upon introduction of the whiskers. The nanocomposite with the best combination of conductivity (1.6 × 10^?4 S/cm at room temperature and a relative humidity of 75%) and Young's modulus (7 MPa) was obtained with a copolymer having an EO‐EPI ratio of 84 : 16, a whisker content of 10% w/w, and a LiClO₄ concentration of 5.8% w/w. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2883–2888, 2004     

Novel copolymers of styrene. 1. Alkyl ring-substituted 2-cyano-3-phenyl 2-propenamides

Novel electrophilic trisubstituted ethylene monomers, alkyl ring-substituted 2-cyano-3-phenyl-2-propenamides, RC₆H₄CH=C(CN)CONH₂ (where R is 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-i-propyl, 4-i-butyl, and 4-t-butyl), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, AIBN at 70 °C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H- and ¹³C-NMR, GPC, DSC, and TGA. High T _g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500 °C range with residue (5–7 wt%), which then decomposed in the 500–800 °C range.     

Synthesis and characterization of poly(oxyethylene)–poly(caprolactone) multiblock copolymers

Novel poly(oxyethylene)/poly(caprolactone) POE/PCL copolymers were synthesized by step growth polymerization of poly(ε-caprolactone) diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. The reaction was performed at room temperature and yielded multiblock copolymers with predetermined POE and PCL block lengths. The resulting copolymers were characterized by various analytical techniques including SEC, IR, ¹H NMR, DSC and X-ray diffractometry. Data showed that the properties of these polymers can be modulated by adjusting the chain lengths of the macromonomers. In particular, one or two crystalline structures can exist within the copolymers of various crystallinities. © 1998 SCI.     

Synthesis and characterization of perfluorinated acrylate–methyl methacrylate copolymers

A novel perfluorinated acrylic monomer 3,5‐bis(perfluorobenzyloxy)benzyl acrylate (FM) with perfluorinated aromatic units was synthesized with 3,5‐bis(perfluorobenzyl)oxybenzyl alcohol, acryloyl chloride, and triethylamine. Copolymers of FM monomer with methyl methacrylate (MMA) were prepared via free‐radical polymerization at 80°C in toluene with 2,2′‐azobisisobutyronitrile as the initiator. The obtained copolymers were characterized by ¹H‐NMR and gel permeation chromatography. The monomer reactivity ratios for the monomer pair were calculated with the extended Kelen–Tüdos method. The reactivity ratios were found to be r₁ = 0.38 for FM, r₂ = 1.11 for MMA, and r₁r₂ < 1 for the pair FM–MMA. This shows that the system proceeded as random copolymerization. The thermal behavior of the copolymers was investigated by thermogravimetric analysis and differential scanning calorimetry (DSC). The copolymers had only one glass‐transition temperature, which changed from 46 to 78°C depending on the copolymer composition. Melting endotherms were not observed in the DSC traces; this indicated that all of the copolymers were completely amorphous. Copolymer films were prepared by spin coating, and contact angle measurements of water and ethylene glycol on the films indicated a high degree of hydrophobicity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hydrolytic degradation of poly(oxyethylene)–poly-(ε-caprolactone) multiblock copolymers

The degradation of poly(oxyethylene)–poly(ε-caprolactone) (POE–PCL) multiblock copolymers was investigated at 37°C in a 0.13M, pH 7.4 phosphate buffer selected to mimic in vivo conditions. The copolymers were obtained by coupling polycaprolactone diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. Various techniques, such as weighing, size exclusion chromatography, infrared, ¹H nuclear magnetic resonance, differential scanning calorimetry, and X-ray diffractometry, were used to monitor changes in total mass, water absorption, molar mass, thermal properties, degree of crystallinity, and composition. The results showed that introduction of POE sequences considerably increased the hydrophilicity of the copolymers as compared with PCL homopolymers. Nevertheless, the degradability of PCL sequences was not enhanced due to the phase separation between the two components. Significant morphological changes were also observed during the degradation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 989–998, 1998     

Synthesis and characterization of multiblock semi-crystalline hydrophobic poly(ether ether ketone)–hydrophilic disulfonated poly(arylene ether sulfone) copolymers for proton exchange membranes

Multiblock copolymers based on alternating segments of telechelic phenoxide terminated hydrophilic fully disulfonated poly(arylene ether sulfone) (BPS100) and decafluorobiphenyl (DFBP) terminated hydrophobic poly(arylene ether ketimine) (PEEKt), were synthesized from the hydrophilic and ketimine-protected amorphous hydrophobic telechelic oligomers by nucleophilic coupling reactions. After film formation from DMSO, the copolymer was acidified, which converted the ketimine to semi-crystalline ketone segments and the sulfonate salts to disulfonic acids. A semi-crystalline phase with a T_m of 325 °C was confirmed. The semi-crystalline multiblock copolymer membranes were tough, ductile and solvent resistant. Fundamental properties as proton exchange membranes (PEMs) showed enhanced conductivities under fully hydrated and reduced humidity conditions. These multiblock copolymers exhibited low in-plane anisotropic swelling behavior, in contrast to the random copolymers.     

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     

Enzyme-catalyzed polymerization and degradation of copolymers prepared from ?-caprolactone and poly(ethylene glycol)

Copolymerizations of ?-caprolactone (CL) with monohydroxyl or dihydroxyl poly(ethylene glycol) (PEG) were successfully performed using Novozyme-435 (immobilized lipase B from Candida antartica) as catalyst. Diblock and triblock copolymers with different compositions were characterized by ¹H NMR, GPC, DSC and X-ray diffraction. The enzymatic copolymerization carried out in toluene presented higher reaction rate and yield than that in bulk. Increasing the [CL]/[EO] feed ratio resulted in increases of molecular weight (M_n) of copolymers. Moreover, the compositions of triblock copolymers were closer to the monomer feed ratios than those of diblock copolymers. The resulting copolymers were all semicrystalline, the crystalline structure being of the PCL type. Solution cast films were allowed to degrade in a pH 7.0 phosphate buffer solution containing Pseudomonas lipase. Weight loss data showed that the introduction of PEG segments to the PCL main chain did not alter the enzymatic degradation of PCL significantly.     

Synthesis, structures and thermal properties of new class epoxide-terminated telechelic poly(2,6-dimethyl-1,4-phenylene oxide)s

Dihydroxyl telechelic poly(2,6-dimethyl-1,4-phenylene oxide)s (1) with regiocontrolled end-group structures have been synthesized by oxidative polymerization of 2,6-dimethylphenol with various aromatic diols in the presence of CuBr/dibutylamine catalysts. The novel one- or two-armed telechelic derivatives based on aromatic diols as core and 1 as arms were subsequently epoxidized with epichlorohydrin and a series of new epoxidized poly(2,6-dimethyl-1,4-phenylene oxide)s (2) were accessible with number average molecular weight ranged from 3500 to 14,000. The end-group structures and regioselectivity of polymers were controlled by the CuBr/dibutylamine catalysts under different reaction conditions, and the structures and properties were studied by nuclear magnetic resonance spectroscopy, gel permeation chromatography, thermogravimetric analysis and differential scanning calorimetry. Upon heating in the presence of oxygen, the one-armed dihydroxyl telechelic polymer was converted via intermolecular coupling and redistribution reaction to the two-armed derivative with significant increase in its molecular weight and elimination of diol monomer. Treatment of dihydroxyl telechelic derivatives with epichlorohydrin and NaOH afforded the epoxide-terminated telechelic derivatives in 77-94% yields.