Synthesis of functional polyethylene graft copolymers by nitroxide‐mediated living radical polymerization

This paper describes a new method to prepare graft copolymers, such as polyethylene‐g‐polystyrene (PE‐g‐PS), with a relatively well‐controlled reaction mechanism. The chemistry involves a transformation process from the metallocene copolymerization of ethylene and m,p‐methylstyrene (m,p‐MS) to nitroxide‐mediated “living” free radical polymerization (LRFP) of styrene. The metallocene catalysis produces ethylene‐co‐m,p‐methylstyrene (EMS) random copolymers. Next, 1‐hydroxyl‐2,2,6,6‐tetramethylpiperidine (HO‐TEMPO) was synthesized by the reduction of TEMPO with sodium ascorbate. The macroinitiator (EMS‐TEMPO) was synthesized with the bromination reaction of EMS, and the following nucleofilic reaction with this functional nitroxyl compound. The resulting macroinitiator (EMS‐TEMPO) for LRFP was then heated in the presence of styrene to form graft copolymer. DSC, ¹H‐NMR, FTIR spectroscopy were employed to investigate the structure of the polymers. The results of Molau test showed that PE‐g‐PS could be a potential good compatilizer. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts

Anionic graft copolymers were synthesized through grafting of poly(ethylene glycol) monomethyl ether (MPEG) onto terpolymers containing succicinic anhydride groups. The backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene, and one of the following monomers: methyl methacrylate, ethylhexyl methacrylate, and diethyl fumarate. MPEG of different molecular weights were grafted onto the backbone through reactions with the cyclic anhydride groups. In this reaction one carboxylic acid group is formed together with each ester bond. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and ¹H-NMR. Thermal properties were examined by DSC. Graft copolymers containing 50% w/w of MPEG 2000 grafts were found to be almost completely amorphous, presumably because of crosslinking, and hydrogen bonding between carboxylic acid groups in the backbone and the ether oxygens in MPEG grafts. © 1995 John Wiley & Sons, Inc.     

Preparation and properties of some water-soluble,comb-shaped,amphiphilic polymers

Water-soluble comb-shaped polymers were prepared through grafting of poly(ethylene glycol) monomethyl ethers (MPEG) onto acrylic and methacrylic ester copolymers by transesterification reactions. The grafting was alkali-catalyzed, and performed in refluxing toluene solution or in melt at 155°C. The grafting efficiency was found to be on the order of 1 graft/10 monomer units. Epoxy groups in glycidyl methacrylate copolymers were also utilized for grafting. The crude graft copolymers were purified through chromatography and characterized by NMR and IR spectroscopy. Polymers prepared from MPEG 2000 were crystalline with melting points 10–15°C lower than the MPEG used. All polymers were shown to be surface active with CMC on the order of 1.5 g/L, and surface tensions of 38–45 dyn/cm. When used as emulsifiers the graft copolymers containing bulky lipophilic ester groups (2-ethylhexyl t-butyl) gave oil-in-water (o/w) and water-in-oil (w/o) emulsions from xylene/water with higher stability than those containing straight chain ester groups (methyl nbutyl n-docecyl). The most stable emulsions were obtained by dissolving the polymers in the organic phase.     

Synthesis of amphiphilic linear‐hyperbranched graft‐copolymers via grafting based on linear polyethylene backbone

The synthesis of amphiphilic linear‐hyperbranched graft‐copolymers in a grafting‐from approach is reported. The linear polyethylene with terminated hydroxyls, prepared by copolymerization of ethylene and 10‐undecen‐1‐ol, was used as macroinitiator for ring‐opening multibranching polymerization of glycidol by a typical slow monomer addition approach. Successful attachment of the hyperbranched grafts to the linear polyethylene backbone was confirmed by ¹H/¹³C NMR, GPC, and TGA. The degree of polymerization and M_w/M_n of hyperbranched grafts were efficiently controlled by temperature, deprotonation ratio as well as the molar ratio of glycidol/hydroxyl (N_glycidol/N_OH). The complicated microstructures caused by unsymmetric glycidol structure were analyzed by DEPT and 2D HSQC spectra, the degree of branching of 0.63–0.66 were calculated, indicating the extent of branch is close to theoretical values. The thermal analysis of linear‐hyperbranched copolymers via TGA and DSC is also presented. To our knowledge, this is the first report of a linear‐hyperbranched graft‐copolymer with a crystalline and nonpolar linear‐polyethylene segment. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2146–2154     

Synthesis and characterization of amphiphilic block–graft MPEG‐b‐(PαN3CL‐g‐alkyne) degradable copolymers by ring‐opening polymerization and click chemistry

A straightforward strategy is proposed for the synthesis of novel, amphiphilic block–graft MPEG‐b‐(PαN₃CL‐g‐alkyne) degradable copolymers. First, the ring‐opening polymerization of α‐chloro‐ε‐caprolactone (αClCL) was initiated by hydroxy‐terminated macroinitiator monomethoxy poly(ethylene glycol) (MPEG) with SnOct₂ as the catalyst. In a second step, pendent chlorides were converted into azides by the reaction with sodium azide. Finally, various kinds of terminal alkynes were reacted with pendent azides by copper‐catalyzed Huisgen's 1,3‐dipolar cycloaddition, and thus a “click” reaction. These copolymers were characterized by differential scanning calorimetry (DSC), ¹H NMR, IR, and gel permeation chromatography. By fixing the length of the MPEG block and increasing the length of PαClCL (or PαN₃CL) block, an increase tendency in T_gs was observed. However, the copolymers of MPEG‐b‐PαClCL and MPEG‐b‐PαN₃CL were semicrystalline when the M_n of MPEG was above 2000 g mol^?1. The block–graft copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 1.4–12.0 mg L^?1 depending on the composition of polymers. The lengths of hydrophilic segment influence the shape of the micelle. The mean hydrodynamic diameters of the micelles from dynamic light scattering were in the range of 90–160 nm. In vitro hydrolytic degradation of block–graft copolymers is faster than the corresponding block copolymers. The drug entrapment efficiency and the drug loading content of micelles depending on the composition of block–graft polymers were described. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4320–4331, 2008     

Synthesis of maleic anhydride grafted polyethylene and polypropylene,with controlled molecular structures

This article discusses a new chemical route to prepare maleic anhydride (MA) grafted polyethylene and polypropylene polymers with controlled molecular structure, that is, MA grafted content and polymer molecular weight and composition distributions. The chemistry involves a free radical graft reaction of maleic anhydride with poly(ethylene‐co‐p‐methylstyrene) and poly(propylene‐co‐p‐methylstyrene) copolymers. Under a suspension reaction condition, the grafting reaction takes place selectively on the p‐methylstyrene units in the copolymer, due to high reactivity of p‐methyl group and favorable mixing between p‐methylstyrene units and chemical reagents in the swollen amorphous phases. The resulting polymer shows no detectable molecular weight change during the reaction, and the MA grafted content increases with the increase of initiator and p‐methylstyrene concentrations. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1337–1343, 2000     

Crystallization behavior and morphology of poly(ethylene‐co‐trimethylene terephthalate)s

The melt crystallization behaviors and crystalline structures of poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate), and poly(ethylene‐co‐trimethylene terephthalate) (PETT) were investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction at various crystallization temperatures (T_cs). The PETT copolymers were synthesized via the polycondensation of terephthalate with ethylene glycol and trimethylene glycol (TG) in various compositions. The copolymers with 69.0 mol % or more TG or 31.0 mol % or less TG were crystallizable, but the other copolymers containing 34–56 mol % TG were amorphous. The DSC isothermal results revealed that the addition of a small amount of flexible TG (up to 21 mol %) to the PET structure slightly reduced the formation of three‐dimensional spherulites. A greater TG concentration (91–100%) in the copolyesters changed the crystal growth from two‐dimensional to three‐dimensional. The DSC heating scans after the completion of isothermal crystallization at various T_cs showed three melting endotherms for PET, PETT‐88, PETT‐84, and PETT‐79 and four melting endotherms for PETT‐9 and PETT. The presence of an additional melting endotherm could be attributed to the melting of thinner and imperfect copolyester crystallites. Analyses of the Lauritzen–Hoffman equation demonstrated that PETT‐88 had the highest values of the product of the lateral and folding surface free energies, and this suggested that the addition of small amounts of flexible trimethylene terephthalate segments to PET disturbed chain regularity, thus increasing molecular chain mobility. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4255–4271, 2004     

聚乙二醇单甲醚(MPEG)/聚乙烯醇(PVA)高分子固-固相变材料的合成与性能

高分子固-固相转变材料是近年来新兴的课题,其主要优点是体积变化小,发生相转变时不出现液态,可以减少对容器的要求,甚至不需要容器即可把相变材料作为结构材料,可简化工艺和降低成本,我们相继合成了系列聚乙二醇／聚乙烯醇高分子固-固相变材料,由于形成交联网络结构,难溶于一般有机溶剂。     

Synthesis of block‐graft polymers by anionic polymerizations

Two poly(4‐methylstyrene) (P4MS)‐block‐polystyrene (PS)‐block‐P4MS triblock copolymers were prepared by successive anionic addition of styrene and 4‐methylstyrene monomers as the core backbone ( CB ) for the architecture of block‐graft polymers. Both terminal 4‐methylstyrene blocks of CB were metalated with a sec‐butyllithium (sec‐BuLi)/tetramethylethylenediamine (TMEDA) complex in cyclohexane. The first‐generation block‐graft polymer ( 1BG ) was prepared by anionic polymerization of α‐methylstyrene by the lithiated CB in tetrahydrofuran (THF) at –78°C and subsequently the terminal graft ends were capped with a small amount of 4‐methylstyrene. The characterization of those block‐graft polymers was carried out in detail.     

Synthesis and properties of fluorine‐containing amphiphilic graft copolymer P(HFMA)‐g‐P(SPEG)

A series of amphiphilic graft copolymers P(HFMA)‐g‐P(SPEG) comprising poly(hexafluorobutyl methacrylate) (PHFMA) backbones and poly(ethylene glycol) (PEG) side chains were synthesized by copolymerization of HFMA and SPEG macromonomer with the p‐vinylbenzyl end group. The SPEG macromonomer was synthesized by reacting Methoxy poly(ethylene glycol) (MPEG) with p‐chloromethylstyrene in THF in the presence of NaH. The macromonomer and amphiphilic graft copolymer were characterized by FTIR, ¹H NMR, ¹⁹F NMR, and gel permeation chromatography (GPC). The critical micelle concentration (CMC) of the amphiphilic graft copolymer was measured by surface tension technique. The results showed that the CMC decreased with increasing HFMA contents in the graft copolymers. The interaction between P(HFMA)‐g‐P(SPEG) and bovine serum albumin (BSA) was studied by fluorescence spectroscopy, transmission electron microscopy (TEM), and photon correlation spectroscopy (PCS). The fluorescence spectrum showed that the fluorescence intensity of BSA increased with increasing content of HFMA in P(HFMA)‐g‐P(SPEG) and concentration of P(HFMA)‐g‐P(SPEG) in the P(HFMA)‐g‐P(SPEG)/BSA solution. TEM micrographs showed that P(HFMA)‐g‐P(SPEG) mainly formed core‐shell structure micelles. When BSA was added, the micelles changed from a core‐shell structure into a worm‐like, vesicle‐like and hollow‐like structure with different initial concentrations of the copolymer. The size distribution of the micelles increased proving that the copolymer micelles encapsulated the bovine serum albumin. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4895–4907, 2009     

Complex,degradable polyester materials via ketoxime ether‐based functionalization: Amphiphilic,multifunctional graft copolymers and their resulting solution‐state aggregates

Degradable, amphiphilic graft copolymers of poly(ε‐caprolactone)‐graft‐poly(ethylene oxide), PCL‐g‐PEO, were synthesized via a grafting onto strategy taking advantage of the ketones presented along the backbone of the statistical copolymer poly(ε‐caprolactone)‐co‐(2‐oxepane‐1,5‐dione), (PCL‐co‐OPD). Through the formation of stable ketoxime ether linkages, 3 kDa PEO grafts and p‐methoxybenzyl side chains were incorporated onto the polyester backbone with a high degree of fidelity and efficiency, as verified by NMR spectroscopies and GPC analysis (90% grafting efficiency in some cases). The resulting block graft copolymers displayed significant thermal differences, specifically a depression in the observed melting transition temperature, T_m, in comparison with the parent PCL and PEO polymers. These amphiphilic block graft copolymers undergo self‐assembly in aqueous solution with the P(CL‐co‐OPD‐co‐(OPD‐g‐PEO)) polymer forming spherical micelles and a P(CL‐co‐OPD‐co‐(OPD‐g‐PEO)‐co‐(OPD‐g‐pMeOBn)) forming cylindrical or rod‐like micelles, as observed by transmission electron microscopy and atomic force microscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3553–3563, 2010     

含mPEG侧链的水溶性梳状聚合物的合成及其侧链受限结晶行为研究

采用大单体与小单体共聚的技术,通过自由基引发溶液聚合,合成了一系列水溶性梳状聚合物———聚丙烯酸接枝聚乙二醇单甲醚(PAA-g-mPEG).制备过程分两步进行,首先合成大单体聚乙二醇单甲醚丙烯酸酯,然后将大单体与丙烯酸单体共聚,合成了梳状聚合物.通过控制反应条件,获得了一系列主链和支链组成比不同的接枝共聚物.用傅立叶变换红外光谱(FT-IR)和核磁共振氢谱(1H-NMR)表征了共聚物的结构,并对其侧链的结晶行为进行了研究.采用差热扫描量热法(DSC)表征并分析了不同侧链长度的mPEG的热性能及其结晶情况.利用相差显微镜和原子力显微镜(AFM)观察薄膜的结晶形貌,表明梳状聚合物的侧链mPEG在受限条件下的薄膜结晶形貌为高度支化的晶体,初步分析了mPEG链长及其在共聚物中的重量百分含量对晶体形貌的影响.     

Homo‐ and Copolymerization of Styrene and Alkylstyrenes with the Highly Active Catalyst System CpTiF3/MAO

Syndiotactic copolymers with p‐methylstyrene, p‐tert‐butylstyrene and α‐methylstyrene were obtained using fluorinated half‐sandwich catalyst systems. In the presence of p‐alkylstyrenes the activities were high. The incorporation of p‐alkylstyrenes is nearly as good as it is for styrene. Molar masses increase using p‐alkylstyrene comonomers. The steric hindrance of the α‐methyl group in α‐methylstyrene results in low activities and poor incorporation rates. Since the melting points of the copolymers are lower than the melting point of the styrene homopolymer the products are easier to process. Crystalline p‐tert‐butylstyrene‐rich copolymers were obtained if appropriate crystallization procedures were carried out.     

含氟两亲接枝共聚物的制备及其结晶行为

采用大分子单体技术合成了一系列以聚乙二醇为支链、甲基丙烯酸六氟丁酯为主链的含氟两亲接枝共聚物(PHFMA-g-PSPEG)。用1HNMR和凝胶色谱(GPC)对制备的大分子单体和两亲接枝共聚物的结构进行了表征。利用示差扫描量热法(DSC)、X射线衍射(XRD)和偏光显微镜(POM)测试技术对含氟两亲接枝共聚物的结晶行为进行了研究。DSC和XRD结果表明,随着共聚物中含氟链段质量分数的增加,其结晶温度(Tc)和结晶度(Xc)均降低,而结晶熔融温度(Tm)先减小后增加。POM发现,随着共聚物中含氟链段质量分数的增加,其结晶速度减慢,共聚物形成清晰球晶的能力减弱,当共聚物中含氟链段质量分数为57%时,含氟两亲接枝共聚物已不能形成清晰的球晶。     

Preparation of methoxy poly(ethylene glycol)/polyester diblock copolymers and examination of the gel‐to‐sol transition

Diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) and poly(?‐caprolactone) (PCL), poly(δ‐valerolactone) (PVL), poly(L ‐lactic acid) (PLLA), or poly(lactic‐co‐glycolic acid) (PLGA) as biodegradable polyesters were prepared to examine the phase transition of diblock copolymer solutions. MPEG–PCL and MPEG–PVL diblock copolymers and MPEG–PLLA and MPEG–PLGA diblock copolymers were synthesized by the ring‐opening polymerization of ?‐caprolactone or δ‐valerolactone in the presence of HCl · Et₂O as a monomer activator at room temperature and by the ring‐opening polymerization of L ‐lactide or a mixture of L ‐lactide and glycolide in the presence of stannous octoate at 130 °C, respectively. The synthesized diblock copolymers were characterized with ¹H NMR, IR, and gel permeation chromatography. The phase transitions for diblock copolymer aqueous solutions of various concentrations were explored according to the temperature variation. The diblock copolymer solutions exhibited the phase transition from gel to sol with increasing temperature. As the polyester block length of the diblock copolymers increased, the gel‐to‐sol transition moved to a lower concentration region. The gel‐to‐sol transition showed a dependence on the length of the polyester block segment. According to X‐ray diffraction and differential scanning calorimetry thermal studies, the gel‐to‐sol transition of the diblock copolymer solutions depended on their degrees of crystallinity because water could easily diffuse into amorphous polymers in comparison with polymers with a crystalline structure. The crystallinity markedly depended on both the distinct character and composition of the block segment. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5784–5793, 2004     

Thermoresponsive PPEGMEA‐g‐PPEGEEMA well‐defined double hydrophilic graft copolymer synthesized by successive SET‐LRP and ATRP

A series of well‐defined double hydrophilic graft copolymers containing poly[poly(ethylene glycol) methyl ether acrylate] (PPEGMEA) backbone and poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) side chains were synthesized by the combination of single electron transfer‐living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained comb copolymer was treated with lithium diisopropylamide and 2‐bromoisobutyryl bromide to give PPEGMEA‐Br macroinitiator. Finally, PPEGMEA‐g‐PPEGEEMA graft copolymers were synthesized by ATRP of poly(ethylene glycol) ethyl ether methacrylate macromonomer using PPEGMEA‐Br macroinitiator via the grafting‐from route. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept narrow (M_w/M_n ≤ 1.20). This kind of double hydrophilic copolymer was found to be stimuli‐responsive to both temperature and ion (0.3 M Cl^? and SO). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 647–655, 2010     

Investigation by combined solid‐state NMR and SAXS methods of the morphology and domain size in polystyrene‐b‐polyethylene oxide‐b‐polystyrene triblock copolymers

The microphase structure of a series of polystyrene‐b‐polyethylene oxide‐b‐polystyrene (SEOS) triblock copolymers with different compositions and molecular weights has been studied by solid‐state NMR, DSC, wide and small angle X‐ray scattering (WAXS and SAXS). WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethylene‐oxide (PEO) blocks at room temperature as a function of the copolymer chemical composition. Furthermore, DSC experiments allowed the determination of the melting temperatures of the crystalline part of the PEO blocks. SAXS measurements, performed above and below the melting temperature of the PEO blocks, revealed the formation of periodic structures, but the absence or the weakness of high order reflections peaks did not allow a clear assessment of the morphological structure of the copolymers. This information was inferred by combining the results obtained by SAXS and ¹H NMR spin diffusion experiments, which also provided an estimation of the size of the dispersed phases of the nanostructured copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 55–64, 2010     

Chitosan-N-poly(ethylene glycol) brush copolymers: Synthesis and adsorption on silica surface

Chitosan-N-poly(ethylene glycol) brush copolymers with different degree of substitution (DS) were synthesized via reductive amination of chitosan by methoxy poly(ethylene glycol) (MPEG) aldehyde. Chitosan-N-MPEG copolymers were high-molecular-weight products with desirable DS; solubility and solution viscosity of those copolymers depended on the method of the synthesis of MPEG aldehyde and on DS. Synthesis of MPEG aldehyde by the use of TEMPO radical/BAIB was not suitable because of partial oxidation of methoxy groups of MPEG resulting in bifunctional PEG derivatives leading to cross-linking. Adsorption studies of chitosan-N-MPEG graft copolymers on silica surface show that these polymers adsorb in highly hydrated layers.     

Synthesis of well‐defined pH‐responsive PPEGMEA‐g‐P2VP double hydrophilic graft copolymer via sequential SET‐LRP and ATRP

A series of well‐defined double hydrophilic graft copolymers containing poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMEA) backbone and poly(2‐vinylpyridine) (P2VP) side chains were synthesized by successive single electron transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate (PEGMEA) macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained homopolymer then reacted with lithium diisopropylamide and 2‐chloropropionyl chloride at ?78 °C to afford PPEGMEA‐Cl macroinitiator. poly(poly(ethylene glycol) methyl ether acrylate)‐g‐poly(2‐vinylpyridine) double hydrophilic graft copolymers were finally synthesized by. ATRP of 2‐vinylpyridine initiated by PPEGMEA‐Cl macroinitiator at 25 °C using CuCl/hexamethyldiethylenetriamine as catalytic system via the grafting‐ from strategy. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept relatively narrow (M_w/M_n ≤ 1.40). pH‐Responsive micellization behavior was investigated by ¹H NMR, dynamic light scattering, and transmission electron microscopy and this kind of double hydrophilic graft copolymer aggregated to form micelles with P2VP‐core while pH of the aqueous solution was above 5.0. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Copolymerization of ethylene with cyclopentene or 2‐butene with half titanocenes‐based catalysts

Half titanocenes (CpCH₂CH₂O)TiCl₂ (1), (CpCH₂CH₂OCH₃)TiCl₃ (2), and CpTiCl₃ (3), activated by methylaluminoxane (MAO) were tested in copolymerization of ethylene with internal olefins such as cyclopentene. All the catalysts were able to give incorporation of cyclopentene in polyethylene matrix. ¹³C NMR analysis of obtained copolymers showed that the catalytic systems have low regiospecificity. In fact, in ethylene–cyclopentene copolymers, cyclic olefin inserts with both 1,2 and 1,3‐enchainment. X‐ray powder diffraction analysis of these copolymers confirmed that 1,2 inserted cyclopentene units are excluded from crystalline phase, whereas 1,3‐cyclopentene units are included, giving rise to expansion of unit cell of crystalline polyethylene. Titanium‐based catalysts were investigated also in the copolymerization of ethylene with E and Z‐2‐butene. Only complex (1) was able to give copolymers and ¹³C NMR analysis of products showed 2‐3, 1‐3, and 1‐2 insertion of 2‐butene. Differential scanning calorimetry analysis displayed that ethylene–cyclopentene, as well as ethylene‐2‐butene, copolymers are crystalline and their melting point decreases by increasing the comonomer content. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4725–4733, 2008