Thermally latent synthesis of networked polymers from multifunctional hemiacetal ester and diepoxide catalyzed by Schiff‐base‐zinc chloride complex

Thermally latent reaction of a copolymer ( P1 ) bearing hemiacetal ester and n‐butyl methacrylate moieties and glycidyl phenyl ether ( 2 ) was catalyzed by bis(p‐methoxybenzylidene)‐1,2‐diiminoethane/zinc chloride complex (ZnCl₂/ 3 ) at 30–150 °C for 6 h. No reaction of P1 and 2 took place below 70 °C, and it smoothly proceeded above 120 °C. The latencies and activities mean that ZnCl₂/ 3 meets both the high latencies at ambient conditions and the high activities at desired temperatures. Thermal crosslinking reaction employing multifunctional derivatives was carried out using ZnCl₂/ 3 at 140 °C for 6 h to afford a networked polymer in high yields. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3682–3689, 2008     

Thermally latent reaction of hemiacetal ester with epoxide catalyzed by recyclable polymeric catalyst consisting of salen‐zinc complex and polyurethane main chain

This article describes the synthesis of and catalysis with a polymeric catalyst (Zn/ 1_NHCOO ) carrying salen‐zinc complex structure in the main chain prepared from polyaddition of zinc/bis(4‐hydroxy)salicylidene‐1,2‐diiminoethane and 4,4′‐diphenylmethane diisocyanate. Poly(Zn/ 1_NHCOO ) promoted the reaction of glycidyl phenyl ether (2) with 1‐propoxyethyl‐2‐ethylhexanoate (3) only at moderately elevated temperatures. Poly(Zn/ 1_NHCOO ) can be recycled by simple filtration from the reaction mixtures, and the recycled polymer is as active as the freshly prepared one. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3673–3681, 2008     

Model reaction for thermally latent curing through addition of hemiacetal ester and epoxide by schiff‐base–zinc halide complexes

Schiff‐base–zinc halide complexes (ZnX₂/ 1 ) thermal‐latently catalyze the reaction of glycidyl phenyl ether (2) and 1‐propoxyethyl 2‐ethylhexanoate (3) that proceeds at moderately elevated temperatures. The catalysis by the ZnX₂/ 1 complexes proceeds via the thermal dissociation of 3 to produce the corresponding carboxylic acid that nucleophilically attacks 2 predominantly over the thermally dissociated vinyl ether. ZnX₂/ 1 complexes catalyze both the dissociation of 3 to produce the carboxylic acid intermediate and its addition to 2 . Although conventional latent catalysts for this reaction exhibit Lewis acidities under ambient conditions that are responsible to the gradual degradation of hemiacetal esters and the polymerization of epoxides, a mixture of 2 , 3 , and ZnX₂/ 1 can be stored for 3 months at ambient conditions. The stored mixture is as active as the freshly prepared mixture, keeping the excellent activity and latency of ZnX₂/ 1 . As well as the model reaction, the thermally latent polyaddition of bisphenol A diglycidyl ether (9) and di‐1‐propoxyethyl adipate (10) is also promoted with ZnCl₂/ 1 at a moderate elevated temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3370–3379, 2007     

Synthesis of polyethers with unsymmetrical structures by the polyaddition of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane with diacyl chlorides

Polyethers with unsymmetrical structures in the main chains and pendant chloromethyl groups were synthesized by the polyaddition of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane (EGMO) with certain diacyl chlorides with quaternary onium salts or pyridine as catalysts. The unsymmetrical polyaddition of EGMO containing two different cyclic ether moieties such as oxirane and oxetane groups with terephthaloyl chloride proceeded smoothly in toluene at 90 °C for 6 h to give polymer 1 with a number‐average molecular weight (M_n) of 51,700 in a 93% yield when tetrabutylammonium bromide (TBAB) was used as a catalyst. The polyaddition also proceeded smoothly under the same conditions when other quaternary onium salts, such as tetrabutylammonium chloride, tetrabutylammonium iodide, tetrabutylphosphonium chloride, and tetrabutylphosphonium bromide, and pyridine were used as catalysts. However, without a catalyst no reaction occurred under the same reaction conditions. Polyadditions of EGMO with isophthaloyl chloride and adipoyl chloride gave polymer 2 (M_n = 28,700) and polymer 3 (M_n = 25,400) in 99 and 65% yields, respectively, under the same conditions. The chemical modification of the resulting polymer, polymer 1 , which contained reactive pendant chloromethyl groups, was also attempted with potassium 3‐phenyl‐2,5‐norbornadiene‐2‐carboxylate with TBAB as a phase‐transfer catalyst, and a polymer with 65 mol % pendant norbornadiene moieties was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 368–375, 2001     

Chain‐growth condensation polymerization of 4‐aminobenzoic acid esters bearing tri(ethylene glycol) side chain with lithium amide base

Chain‐growth condensation polymerization of p‐aminobenzoic acid esters 1 bearing a tri(ethylene glycol) monomethyl ether side chain on the nitrogen atom was investigated by using lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) as a base. The methyl ester monomer 1a afforded polymer with low molecular weight and a broad molecular weight distribution, whereas the polymerization of the phenyl ester monomer 1b at ?20 °C yielded polymer with controlled molecular weight (M_n = 2800–13,400) and low polydispersity (M_w/M_n = 1.10–1.15). Block copolymerization of 1b and 4‐(octylamino)benzoic acid methyl ester ( 2 ) was further investigated. We found that block copolymer of poly 1b and poly 2 with defined molecular weight and low polydispersity was obtained when the polymerization of 1b was initiated with equimolar LiHMDS at ?20 °C and continued at ?50 °C, followed by addition of 2 and equimolar LiHMDS at ?10 °C. Spherical aggregates were formed when a solution of poly 1b in THF was dropped on a glass plate and dried at room temperature, although the block copolymer of poly 1b and poly 2 did not afford similar aggregates under the same conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1357–1363, 2010     

Synthesis and properties of blue light‐emitting,silicon‐containing,regio‐ and stereoregular conjugated polymers

This article concerns the hydrosilylation polyaddition of 1,4‐bis(dimethylsilyl)benzene ( 1 ) with 4,4′‐diethynylbiphenyl, 2,7‐diethynylfluorene ( 2b ), and 2,6‐diethynylnaphthalene with RhI(PPh₃)₃ catalyst. Trans‐rich polymers with weight‐average molecular weights (M_w's) ranging from 19,000 to 25,000 were obtained by polyaddition in o‐Cl₂C₆H₄ at 150–180 °C, whereas cis‐rich polymers with M_w's from 4300 to 34,000 were obtained in toluene at 0 °C–r.t. These polymers emitted blue light in 4–81% quantum yields. The cis polymers isomerized into trans polymers upon UV irradiation, whereas the trans polymers did not. The device having a layer of polymer trans‐ 3b obtained from 1 and 2b demonstrated electroluminescence without any dopant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2774–2783, 2004     

Protective encapsulation of acid‐sensitive catalysts using polyethylene ligands

The stability of polyethylene oligomer (PE_Olig)‐entrapped salen‐metal complexes toward acidolysis is described. These complexes dissolve in hot toluene and precipitate as hydrophobic powders. The salen species in these precipitates or in precipitates of admixtures of oligomeric complexes and unfunctionalized polyethylene are stable to acid when suspended in acidic methanol for 24 h at 25°C. The lack of metal leaching due to acid‐promoted demetalation was determined using both colorimetric and ICP‐MS analyses. The ICP‐MS results showed the amount of metal loss for PE_Olig‐salen‐metal complexes was 0.27%, 0.45%, and 0.79% for half‐salen Cr(III), salen Cr(III), and salen Mn(III) complexes, respectively. These results were in contrast to the reported behavior of low molecular weight salen metal complexes and to results seen with a salen complex bound to divinylbenzene (DVB) crosslinked polystyrene which demetalates under acidic conditions at room temperature. Salen complexes formed with PE_Olig complexes also demetalate when the PE_Olig‐bound species are in solution at elevated temperature and exposed to acid. These results show that as solids oligomeric polyethylene ligands even without added PE can serve as a protective encapsulating matrix for the solid forms of polymer‐supported catalysts. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Efficient zinc initiators supported by NNO‐tridentate ketiminate ligands for cyclic esters polymerization

A series of zinc benzylalkoxide complexes, [LⁿZn(μ‐OBn)]₂ (L = L ¹ H – L ⁵ H ), supported by NNO‐tridentate ketiminate ligands with various electron withdrawing‐donating subsituents have been synthesized and characterized. X‐ray crystal structural studies revealed that complexes 2b and 4b are dinuclear bridging through the benzylalkoxy oxygen atoms with penta‐coordinated metal centers. All the metal complexes have acted as efficient initiators for the ring‐opening polymerization of L ‐lactide (within 12 min, 0 °C). Remarkably, a molecular weight of PLLA up to 580,000 can be achieved using [(L⁵Zn(μ‐OBn)]₂ ( 5b ) as an initiator. The kinetic studies for the polymerization of L ‐lactide with complex 3b at ?10 °C corresponded to first‐order reactions in the monomer. The ring‐opening polymerization (ROP) of ε‐caprolactone, ε‐decalactone, β‐butyrolactone and their copolymer with complex 3b was investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Novel thermally latent self‐crosslinkable copolymers bearing oxetane and hemiacetal ester moieties: The synthesis,self‐crosslinking behavior,and thermal properties

Novel thermally latent self‐crosslinkable copolymers ( 14 and 15 ) containing hemiacetal ester and oxetane moieties were synthesized by the radical copolymerizations of 1‐propoxyethyl methacrylate, 3‐ethyl‐3‐methacryloyloxymethyl oxetane, and/or n‐butyl methacrylate at 60 °C in the presence of 2,2′‐azoisobutylonitrile as an initiator. The obtained copolymers showed good solubility for common organic solvents such as tetrahydrofuran, chloroform, and dimethyl sulfoxide (DMSO). The thermal crosslinking behaviors were examined with several Lewis acid catalysts ( 6 ). In particular, the treatment with aluminum‐2‐ethylhexanate triethanolamine complex ( 6c ) at 160 °C was found to efficiently yield the corresponding self‐crosslinked polymers ( 14′ and 15′ ). Incidentally, the resulting products were hardly insoluble in various organic solvents, including DMSO. The thermal properties of the obtained self‐crosslinked polymers 14′ and 15′ were estimated by thermogravimetric analysis and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4260–4270, 2005     

Rigid triol and diol with adamantane‐like core derived from naturally occurring myo‐inositol and their polyaddition with diisocyanates

Two orthoester derivatives 1 and 2 that are easily accessible from naturally occurring myo‐inositol were exploited as new triol‐ and diol‐type monomers bearing a rigid adamantane‐like structure to polyaddition with diisocyanates that gave the corresponding networked and linear polyurethanes. DSC analysis of the networked polyurethanes revealed their high glass transition temperatures ranging from 155 to 248 °C, suggesting the contribution of the rigidity of the adamantane‐like structure introduced at the nodes of the networked polyurethanes 6. Besides, the polyaddition of 2 with diisocyanates gave the corresponding linear polyurethanes 4, of which glass transition temperatures were high, ranging from 105 to 177 °C, presumably by virtue of the rigidity of the adamantane‐like structure introduced into the main chains. T_gs of the networked polyurethanes 6 were higher than those of the linear polyurethanes 4. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3498–3505     

Novel synthesis of reactive polycarbonates with pendant chloromethyl groups by the polyaddition of bis(oxetane)s with 2,2′‐bis[(4‐chloroformyl)oxyphenyl]propane

The polyaddition of 1,4‐bis[(3‐ethyl‐3‐oxetanyl)methoxymethyl]benzene with 2,2′‐bis[(4‐chloroformyl)oxyphenyl]propane was examined with quaternary onium salts as catalysts. When the polyaddition was carried out with tetrabutylphosphonium bromide in chlorobenzene at 120 °C for 24 h, the corresponding poly(alkyl aryl carbonate) with a high molecular weight (number‐average molecular weight = 16,700) was obtained in an almost quantitative yield. It was found from the ¹H NMR and ¹³C NMR spectra of the obtained polymer that the addition reaction proceeded without any side reactions, providing the polycarbonate with pendant chloromethyl groups in the side chain. The polyaddition of bis{[3‐(3‐ethyloxetanyl)]methyl}terephthalate also proceeded smoothly and gave the corresponding polycarbonate with high molecular weight in a good yield. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2304–2311, 2003     

Radical copolymerization of chlorotrifluoroethylene with 4‐bromo‐3,3,4,4‐tetrafluorobut‐1‐ene

The radical copolymerization of chlorotrifluoroethylene (CTFE) with 3,3,4,4‐tetrafluoro‐4‐bromobut‐1‐ene (BTFB) initiated by tert‐butylperoxypivalate is presented. The microstructures of the obtained copolymers are determined by means of NMR spectroscopies and elemental analysis and show that random copolymers were obtained. A wide range of poly(CTFE‐co‐BTFB) copolymers is synthesized, containing from 17 to 89 mol % of CTFE. In all the cases, CTFE is the less reactive of both comonomers. T_d^10% values, ranging from 163 up to 359 °C, are dependent on the BTFB content. These variations of thermal property are attributed to the increase in the number of C‐H and C‐Br bonds breakdown when the BTFB molar percentage in the copolymer is higher. T_g values range from 19 to 39 °C and a decreasing trend is observed when increasing the amount of BTFB in the copolymer. This observation arises from the higher flexibility of the copolymer when increasing the number of fluorobrominated lateral chains. These original fluoropolymers bearing reactive pendant bromo groups are suitable candidates for various applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1714–1720     

Dichlorovanadium (IV) complexes with salen‐type ligands for ethylene polymerization

Vanadium complexes with tetradentate salen‐type ligands were first time explored in ethylene polymerizations. The effects of the vanadium complex structure, the alkyl aluminum cocatalysts type (EtAlCl₂, Et₂AlCl, Et₃Al, and MAO), and the polymerization conditions (Al/V molar ratio, temperature) on polyethylene yield were explored. It was found that EtAlCl₂ in conjunction with investigated vanadium complexes produced the most efficient catalytic systems. It was shown, moreover, that the structural changes of the tetradentate salen ligand (type of bridge which bond donor nitrogen atoms and type of substituent on aryl rings) affected activity of the catalytic system. The complexes containing ligands with cyclohexylene bridges were more active than those with ethylene bridges. Furthermore, the presence of electron‐withdrawing groups at the para position and electron‐donating substituents at the ortho position on the aryl rings of the ligands resulted in improved activity in relation to the systems with no substituents (with the exception of bulky t‐Bu group). The results presented also revealed that all vanadium complexes activated by common organoaluminum compounds gave linear polyethylenes with high melting points (134.8–137.6 °C), high molecular weights, and broad molecular weight distribution. The polymer produced in the presence of MAO possesses clearly lower melting point (131.4 °C) and some side groups (around 9/1000 C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6940–6949, 2008     

Synthesis of head‐to‐tail polyurethanes from nonsymmetric diisocyanate and ethylene glycol with organotin catalysts

An ordered head‐to‐tail (HT) polyurethane was successfully prepared by the polyaddition reaction of p‐isocyanatobenzyl isocyanate with ethylene glycol with dibutyltin dilaurate as a catalyst. Furthermore, the HT regularity of polyurethane was improved to 83% with 1,1,3,3‐tetraphenyl‐1,3‐dichlorodistannoxane. The polymerization was conducted in N,N‐dimethylformamide at 30 °C with both monomers mixed at once. The microstructure of the polymer was investigated by ¹H and ¹³C NMR spectroscopy, and the polymer obtained by the polyaddition reaction had the expected HT linkages. The constitutional regularity of the polymers influenced the thermal properties and crystallinity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 416–429, 2001     

Three‐component polyaddition of diamines,carbon disulfide,and diacrylates in water

The three‐component polyaddition of diamines, carbon disulfide (CS₂), and diacrylates in water was successfully achieved without the use of a surfactant or catalyst. Appropriate reaction conditions (i.e., reaction temperature, reaction time, and CS₂ feed) enabled the polyaddition of 1,3‐di‐4‐piperidylpropane ( 1a ), CS₂, and 1,6‐hexanediol diacrylate ( 2a ) to afford the corresponding poly(dithiourethane‐amine) containing 83% of dithiourethane units in 84% yield. Polyaddition of other monomers also proceeded under the optimum conditions to afford various poly(dithiourethane‐amine)s. Unsuccessful results for polyaddition in organic solvents such as toluene, tetrahydrofuran, and N,N‐dimethylformamide revealed that the polyaddition is accelerated in water. The obtained poly(dithiourethane‐amine)s adsorbed Au (III) efficiently under acidic conditions, due to the strong interaction of the thiocarbonyl sulfur in the dithiourethane unit with Au (III). The poly(dithiourethane‐amine)s also showed selective adsorption for Au (III) from a mixture of metal ions [Au (III), Fe (III), Mn (II), and Zn (II)], which indicates their potential utilization for the collection of gold. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 845–851, 2010     

Synthesis and properties of new hydroxyl‐pendant aromatic polyimides derived from trimethylsilylated 4,4′‐diamino‐3,3′‐dihydroxybiphenyl and aromatic tetracarboxylic dianhydrides

New phenolic hydroxyl‐pendant aromatic polyimides were synthesized with the N‐silylated diamine method in two steps: the ring‐opening polyaddition of tetrakis(trimethylsilyl)‐substituted 4,4′‐diamino‐3,3′‐dihydroxybiphenyl to various aromatic tetracarboxylic dianhydrides, giving trimethylsiloxy‐pendant poly(amic acid) trimethylsilyl esters, and thermal imidization. The hydroxyl‐bearing polyimides were amorphous but insoluble in organic solvents. They had glass‐transition temperatures greater than 370 °C and temperatures of 10% weight loss greater than 415 °C in nitrogen. The hydroxyl‐pendant polypyromellitimide film had a high tensile strength and a high modulus of 310 MPa and 10 GPa, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1790–1795, 2002     

Di‐nuclear zinc complexes containing tridentate imino‐benzotriazole phenolate derivatives as efficient catalysts for ring‐opening polymerization of cyclic esters and copolymerization of phthalic anhydride with cyclohexene oxide

Zinc catalysts incorporated by imino‐benzotriazole phenolate ( IBTP ) ligands were synthesized and characterized by single‐crystal X‐ray structure determinations. The reaction of the ligand precursor ( ^C1DMeIBTP ‐H or ^C1DIPIBTP ‐H) with diethyl zinc (ZnEt₂) in a stoichiometric proportion in toluene furnished the di‐nuclear ethyl zinc complexes [(μ‐ ^C1DMeIBTP )ZnEt]₂ ( 1 ) and [(μ‐ ^C1DIPIBTP )ZnEt]₂ ( 2 ). The tetra‐coordinated monomeric zinc complex [( ^C1PhIBTP )₂Zn] ( 3 ) or [( ^C1BnIBTP )₂Zn] ( 4 ) resulted from treatment of ^C1PhIBTP ‐H or ^C1BnIBTP ‐H as the pro‐ligand under the similar synthetic method with ligand to metal precursor ratio of 2:1. Single‐crystal X‐ray diffraction of bimetallic complexes 1 and 2 indicates that the ^C1DMeIBTP or ^C1DIPIBTP fragment behaves a NON‐tridentate ligand to coordinate two metal atoms. Catalysis for ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL), β‐butyrolactone (β‐BL), and lactide (LA) of complexes 1 and 2 was systematic studied. In combination with 9‐anthracenemethanol (9‐AnOH), Zn complex 1 was found to polymerize ε‐CL, β‐BL, and L‐LA with efficient catalytic activities in a controlled character. This study also compared the reactivity of these ROP monomers with different ring strains by Zn catalyst 1 in the presence of 9‐AnOH. Additionally, Zn complex 1 combining with benzoic acid was demonstrated to be an active catalytic system to copolymerize phthalic anhydride and cyclohexene oxide. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 714–725     

Polymerization of β‐pinene with Schiff‐base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(β‐pinene) at high temperature with high productivity

A series of easily accessible and stable Schiff‐base nickel complexes (complex 1 – 4 ) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight β‐pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of β‐pinene (M_n ～ 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 10⁷ g polyβ‐pinene/mol of Ni. ¹H NMR analyses showed that the obtained β‐pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff‐base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739–3746, 2007     

Synthesis of polyacetals with various main‐chain structures by the self‐polyaddition of vinyl ethers with a hydroxyl function

To establish the optimum conditions for obtaining high molecular weight polyacetals by the self‐polyaddition of vinyl ethers with a hydroxyl group, we performed the polymerization of 4‐hydroxybutyl vinyl ether (CH₂?CH? O? CH₂CH₂CH₂CH₂? OH) with various acidic catalysts [p‐toluene sulfonic acid monohydrate, p‐toluene sulfonic anhydride (TSAA), pyridinium p‐toluene sulfonate, HCl, and BF₃OEt₂] in different solvents (tetrahydrofuran and toluene) at 0 °C. All the polymerizations proceeded exclusively via the polyaddition mechanism to give polyacetals of the structure [? CH(CH₃)? O? CH₂CH₂CH₂CH₂? O? ]_n quantitatively. The reaction with TSAA in tetrahydrofuran led to the highest molecular weight polymers (number‐average molecular weight = 110,000, weight‐average molecular weight/number‐average molecular weight = 1.59). 2‐Hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, cyclohexane dimethanol monovinyl ether, and tricyclodecane dimethanol monovinyl ether were also employed as monomers, and polyacetals with various main‐chain structures were obtained. This structural variety of the main chain changed the glass‐transition temperature of the polyacetals from approximately ?70 °C to room temperature. These polyacetals were thermally stable but exhibited smooth degradation with a treatment of aqueous acid to give the corresponding diol compounds in quantitative yields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4053–4064, 2002     

Effect of an alkyl substituted in salen ligands on 1,4‐Cis selectivity and molecular weight control in the polymerization of 1,3‐butadiene with (salen)Co(II) complexes in combination with methylaluminoxane

The effect of an alkyl substituted in the aromatic ring of the salen ligand on the polymerization of butadiene (Bd) with (salen)Co(II) complexes in combination with methylaluminoxane (MAO) was investigated. The activity for the polymerization of Bd was influenced significantly by the introduction of alkyl groups at the 3,3′,5,5′‐positions in the aromatic ring of the salen ligand, and both the polymerization rate and 1,4‐cis contents increased in the following order with respect to the alkyl group: H < CH₃ < t‐C₄H₉. This is in good agreement with the bulkiness of the alkyl groups. The activity for the polymerization of the (salen)Co(II) complex possessing t‐C₄H₉ at the 3,3′‐positions was higher than that of the (salen)Co(II) bearing t‐C₄H₉ at the 5,5′‐positions. Thus, the introduction of bulky substituents at the 3,3′‐positions of the salen ligand was an important factor in achieving both high activity and high 1,4‐cis selectivity in the polymerization of Bd with (salen)Co(II) complexes in combination with MAO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4088–4094, 2006