In situ formation of Sn(IV) catalyst with increased activity in ε‐caprolactone and L‐lactide polymerization using stannous(II) 2‐ethylhexanoate

Ring‐opening polymerization (ROP) of ε‐caprolactone and L‐lactide (LA) was studied using stannous(II) 2‐ethylhexanoate (Sn(Oct)₂) with N,N‐dimethylformamide‐dimethyl acetal (DMF‐DMA). DMF‐DMA showed a tenfold improvement in catalytic activity over that of Sn(Oct)₂ under the same conditions. It also enhanced the capability to control molecular weight in the synthesis of small molecular weight polymers of polycaprolactone and polylactide (PLA). The high molecular weight polymerization demonstrated a strong capability to control molecular weight for the polymerization of LA: a molecular weight of PLA exceeding 400,000 was obtained at very low catalytic loadings. The individual polymerization rates of other tin reagents with DMF‐DMA also clearly increased. Applying this methodology could drastically reduce the time and cost required for the fabrication of these products to increase the competitive advantage of manufacturers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and properties of high‐molecular‐weight stereo di‐block polylactides with nonequivalent D/L ratios

Di‐stereoblock polylactides (di‐sb‐PLA: PLLA‐b‐PDLA) having high molecular weight (M_n > 100 kDa) were successfully synthesized by two‐step ring‐opening polymerization (ROP) of L ‐ and D ‐lactides using tin(2‐ethylhexanoate) as a catalyst. By optimizing the polymerization conditions, the block sequences were well regulated at non‐equivalent feed ratios of PLLA and PDLA. This synthetic method consisted of three stages: (1) polymerization of either L ‐ or D ‐lactide to obtain a PLLA or PDLA prepolymer with a molecular weight less than 50 kDa, (2) purification of the obtained prepolymer to remove residual lactide, and (3) polymerization of the enantiomeric lactide in the presence of the purified prepolymer. Their ¹³C and ³¹P NMR spectra of the resultant di‐sb‐PLAs strongly supported their di‐stereo block structure. These di‐sb‐PLAs, having weight‐average molecular weights higher than 150 kDa, were fabricated into polymer films by solution casting and showed exclusive stereocomplexation. The thermomechanical analysis of the films revealed that their heat deformation temperature was limited probably because of their low crystallinity owing to the non‐equivalent PLLA/PDLA ratio. The blend systems of the di‐sb‐PLAs having complementary stereo‐sequences (the one with a long PLLA block and the other with long PDLA block) were also prepared and characterized to enhance the sc crystallinity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 794–801, 2010     

Synthesis of 4μ‐PS2PEO2, 4μ‐PS2PCL2, 4μ‐PI2PEO2, and 4μ‐PI2PCL2 star‐shaped copolymers by the combination of glaser coupling with living anionic polymerization and ring‐opening polymerization

4μ‐A₂B₂ star‐shaped copolymers contained polystyrene (PS), poly(isoprene) (PI), poly(ethylene oxide) (PEO) or poly(ε‐caprolactone) (PCL) arms were synthesized by a combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). Firstly, the functionalized PS or PI with an alkyne group and a protected hydroxyl group at the same end were synthesized by LAP and then modified by propargyl bromide. Subsequently, the macro‐initiator PS or PI with two active hydroxyl groups at the junction point were synthesized by Glaser coupling in the presence of pyridine/CuBr/N,N,N ′,N ″,N ″‐penta‐methyl diethylenetri‐amine (PMDETA) system and followed by hydrolysis of protected hydroxyl groups. Finally, the ROP of EO and ε‐CL monomers was carried out using diphenylmethyl potassium (DPMK) and tin(II)‐bis(2‐ethylhexanoate) (Sn(Oct)₂) as catalyst for target star‐shaped copolymers, respectively. These copolymers and their intermediates were well characterized by SEC, ¹H NMR, MALDI‐TOF mass spectra and FT‐IR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Bulk polymerization of p‐dioxanone using a cyclic tin alkoxide as initiator

Poly(p‐dioxanone) with an inherent viscosity of over 1 dL/g has been synthesized using the cyclic tin alkoxide 1‐di‐n‐butyl‐1‐stanna‐2,5‐dioxacyclopentane as initiator. Poly(p‐dioxanone) was synthesized in bulk and the results have been compared with polymerizations using tin (II) 2‐ethylhexanoate (Sn(Oct)₂) as catalyst. Sn(Oct)₂ has often been reported to be an effective catalyst for the synthesis of poly(p‐dioxanone), but here it is compared with an initiator which is less prone to catalyze transesterification reactions. The results demonstrate that the cyclic tin initiator is a promising alternative for the synthesis of poly(p‐dioxanone) with a high inherent viscosity. Poly(p‐dioxanone) is a polymer with mechanical properties and a degradation rate suitable for tissue engineering applications. Both the cyclic tin initiator and Sn(Oct)₂ gave, under some reaction conditions, inherent viscosities around 1 dL/g. The best polymer synthesized using the cyclic tin initiator had a strain‐at‐break of 515% and a stress‐at‐break of 43 MPa. The inherent viscosity of this polymer was 1.16 dL/g, while Sn(Oct)₂ resulted in a polymer with an inherent viscosity less than 0.4 dL/g under the same reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5552–5558, 2007     

Microwave‐assisted graft polymerization of ε‐caprolactone onto magnetite

The graft polymerization of ε‐caprolactone (ε‐CL) onto magnetite was carried out under microwave irradiation in the presence of tin(II) 2‐ethylhexanoate. The molar ratio of ε‐CL to tin(II) 2‐ethylhexanoate was 300, whereas the molar ratio of ε‐CL to magnetite was 5. The chemical structures of the obtained poly(ε‐caprolactone) coated magnetic nanoparticles were characterized by FTIR and XPS spectroscopy. These magnetic‐polymer hybrid nanostructures were further investigated by X‐ray diffraction and magnetization measurements. The morphology of the magnetic core‐shell nanostructures were determined by TEM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5397–5404, 2009     

Propylene polymerization by C1‐symmetric {ONNO′}‐type salan zirconium complexes

The activities of C₁‐symmetric dibenzyl zirconium complexes of Salan ligands that bear a halo‐substituted phenolate ring and an alkyl‐substituted phenolate ring in propylene polymerization with methylaluminoxane as cocatalyst were studied. These {ONNO′}ZrBn₂‐type catalysts exhibited moderate‐to‐high activities and yielded polypropylene of low molecular weight. The degree of tacticity was found to depend on the steric bulk of the substituents on both phenolate rings and ranged from practically atactic to substantially isotactic (74–78% [mmmm] for polymerizations at room temperature by Lig⁵ZrBn₂). Hemi‐isotactic polypropylene was not obtained, despite the diastereotopicity of the two positions. The pattern of stereo errors was consistent with the enantiomorphic site control of propylene insertion typically observed for C₂‐symmetric catalysts and implied a facile site‐averaging mechanism. A regular 1,2‐insertion and a β‐H transfer to an incoming monomer correspond to the main propagation and termination processes, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Atom transfer radical polymerization using activators regenerated by electron transfer of acrylonitrile in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate

Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile (AN) was first approached with 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium tetrafluoroborate ([ecemim][BF₄]) as reaction medium and tin(II) bis(2‐ethylhexanoate) (Sn(EH)₂) as reducing agent in the presence of air. When compared with in bulk, an obvious increase of polymer isotacticity was observed for ARGET ATRP of AN in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate ([ecemim][PF₆]), the reaction rate of ARGET ATRP of AN in [ecemim][PF₆] was higher and the polymerization process was better controlled. The block copolymer polyacrylonitrile‐block‐poly(methyl methacrylate) with molecular weight at 69,750, distribution at 1.34, and isotacticity at 0.36 was successfully obtained in [ecemim][PF₆]. [Ecemim][PF₆] and the catalyst system were recycled and reused and had no effect on the living nature of polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Organometallic and enzymatic catalysis for ring opening copolymerization of ε‐caprolactone and 4‐methyl‐ε‐caprolactone

A series of copolymers containing ε‐caprolactone (CL) and 4‐methyl‐ε‐caprolactone (MeCL) were synthesized by ring‐opening polymerization (ROP) using Tin(II) bis(2‐ethylhexanoate)(Sn(Oct)₂) or Novozym 435 as catalyst. The molecular structure and weight of copolymers were determined by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC), respectively. Our kinetic study showed that the monomer reactivity ratios for CL (r₁) and MeCL (r₂) using Sn(Oct)₂ as catalyst were estimated to be near unity and r₁ × r₂ = 1, indicating the random distribution of the monomers in the final copolymer. The results of DSC and XRD consistently indicated that the copolymers were inclined to be amorphous with the increasing of MeCL fraction. Microspheres were prepared from copolymers and characterized by SEM. The preliminary degradability and biocompatibility studies on these copolymers were also assessed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of a novel macroinimer based on thiophene and poly(ε‐caprolactone) and its use in electrochromic device application

Synthesis of a novel macroinimer comprising poly(ε‐caprolactone) (PCL) and thiophene (Th) and its use in electrochromic device (ECD) application have been reported. First, a novel Th monomer ( 5 ) with miktofuntional initiator groups (primary hydroxyl and tertiary bromide at the third position of the thiophene ring) was synthesized in a four‐step reaction sequence. Density functional theory‐predicted bond lengths, angles, and vibrations of 5 were in good agreement with available experimental vibrational spectra. Subsequently, ring‐opening polymerization of ε‐caprolactone (ε‐CL) was carried out in bulk using 5 as the initiator and tin(II) 2‐ethylhexanoate (Sn(Oct)₂) as the catalyst at 115 °C, which led to α‐thiophene end‐capped PCL macroinimer (PCL‐Th). Furthermore, PCL‐Th macroinimer was used in electrochemical copolymerization with pyrrole (Py) and Th. PCL‐Th/PTh copolymer film synthesized on indium tin oxide‐coated glass slide showed electrochromic behavior. Optical analyses of the PCL‐Th/PTh copolymer film indicated that the copolymer film was suitable to be used as an anodically coloring material for ECD applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Ring‐opening metathesis polymerization of cis‐cyanocyclooct‐4‐ene: Search for active catalysts,variation of monomer to catalyst ratios and monomer concentrations

The ring‐opening metathesis polymerization (ROMP) of cis‐cyanocyclooct‐4‐ene initiated by ruthenium‐based catalysts of the first, second, and third generation was studied. For the polymerization with the second generation Grubbs catalyst [RuCl₂(?CHPh)(H₂IMes)(PCy₃)] (H₂IMes = N,N′‐bis(mesityl)‐4,5‐dihydroimidazol‐2‐ylidene), the critical monomer concentration at which polymerization occurs was determined, and variation of monomer to catalyst ratios was performed. For this catalyst, ROMP of cis‐cyanocyclooct‐4‐ene did not show the features of a living polymerization as M_n did not linearly increase with increasing monomer conversion. As a consequence of slow initiation rates and intramolecular polymer degradation, molar masses passed through a maximum during the course of the polymerization. With third generation ruthenium catalysts (which contain 3‐bromo or 2‐methylpyridine ligands), polymerization proceeded rapidly, and degradation reactions could not be observed. Contrary to ruthenium‐based catalysts of the second and third generation, a catalyst of the first generation was not able to polymerize cis‐cyanocyclooct‐4‐ene. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Simultaneous reversible addition fragmentation chain transfer and ring‐opening polymerization

The simultaneous ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and 2‐hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ε‐CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2‐ethylhexanoate (Sn(Oct)₂) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA‐g‐PCL. Graft copolymer formation is evidenced by a combination of size‐exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000–10,000 g mol^?1) the copolymer grafting density is higher than 90%. The ratio of free HEMA‐PCL homopolymer produced during the “one‐step” process was found to depend on the HEMA concentration, as well as the half‐life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058–3067, 2008     

Cyclometalated 2‐phenylpyridine complex [RuII(o‐C6H4‐py)(MeCN)4]PF6 as a tunable catalyst for living radical polymerization

The cyclometalated complex [Ru^II(o‐C₆H₄‐py)(MeCN)₄]PF₆ ( 1 ) with a σ‐Ru? C bond and four substitutionally labile acetonitrile ligands mediates radical polymerization of different vinyl monomers, viz. n‐butyl acrylate, methyl methacrylate, and styrene, initiated by three alkyl bromides: ethyl 2‐bromoisobutyrate, methyl 2‐bromopropionate, and 1‐phenylethyl bromide. The polymerization requires the presence of Al(OiPr)₃ and occurs uncontrollably as a conventional radical process. The variation of the molar ratio of the components of the reaction mixture, such as initiator, Al(OiPr)₃ and catalyst, affected the polymerization rates and the molecular weights but did not improve the control. A certain level of control has been achieved by adding 0.5 eq of SnCl₂ as a reducing agent. Tin(II) chloride decreased the rate of polymerization and simultaneously the molecular weights became conversion‐dependent and the polydispersities were also narrowed. Remarkably, the level of control was radically improved in the presence of excess of the poorly soluble catalyst ( 1 ), when the added amount of ( 1 ) was not soluble any more, i.e., under heterogeneous conditions, the system became adjustable and the living polymerization of all three monomers was finally achieved. Possible mechanisms of the ( 1 )‐catalyzed polymerization are discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4193–4204, 2008     

Oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with dinuclear‐type copper(II) catalyst

The oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with the novel dinuclear‐type copper(II) catalysts successfully produced poly(2,3‐dihydroxy‐1,4‐naphthylene). For example, the MeOH‐insoluble polymer with a number average molecular weight of 4.4 × 10³ from the polymerization using the complex of CuCl₂ and N,N′‐bis(2‐morpholinoethyl)‐p‐xylylenediamine ( p ‐ 1 ) at room temperature under an O₂ atmosphere followed by acetylation of the hydroxyl groups was obtained in 63% yield. The structures of the tetraamine ligands and the counter anion of the copper(II) salts significantly influenced the catalyst activity. The polymerization of 2,2′‐dimethoxy‐1,1′‐binaphthalene‐3,3′‐diol with the 2CuCl₂‐ p ‐ 1 catalyst, however, resulted in a lower yield. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1635–1640, 2005     

Synthesis and characterizations of bis(phenoxy)‐amine tin(II) complexes for ring‐opening polymerization of lactide

A series of tin(II) complexes supported by N₂O₂ bis(phenol)‐amine ligands were prepared from the reactions of the corresponding ligands with Sn[N(SiMe₃)₂]₂ in benzene at room temperature. The ligands were designed to have different substituted group at the ortho‐position on the aryl rings (R = ^tBu, CH₃) and N‐containing side arm (E = ? CH₂NEt₂ and pyridine) giving a variation of tin(II) complexes (R = ^tBu, E = CH₂NEt₂, 2a ; R = ^tBu, E = py, 2b ; R = CH₃, E = CH₂NEt₂, 2c ; R = CH₃, E = py, 2d ). All complexes were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. The single‐crystal X‐ray crystallography revealed that all complexes have a monomeric four‐coordinate tin center with a distorted seesaw structure. All complexes are active for solvent‐free polymerization of l ‐lactide at 120 °C giving poly(l ‐lactide) with narrow to moderate dispersity (Ð = 1.12–1.56). In the presence of benzyl alcohol during the polymerization, the resulting polymer was found to be linear having benzyl alcohol as the end group while, in the absence of benzyl alcohol, the polymer was cyclic. The large ^tBu group at the ortho‐position was found to decrease polymerization activity while the more basic ? CH₂NEt₂ group was found to increase the polymerization activity. The polymerization of rac‐lactide under a similar condition gave PLA having a slight heterotactic bias for all catalysts. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2104–2112     

Active‐center equilibrium in Ziegler–Natta butadiene polymerization

The Ziegler–Natta‐catalyzed polymerization of 1,3‐butadiene was investigated at a low aluminum alkyl/cobalt (Al/Co) ratio using two different soluble catalyst systems: cobalt(II) octanoate/diethylaluminum chloride/water and cobalt(II) octanoate/methylaluminoxane/tert‐butyl chloride. When the active‐center concentration was determined by the number‐average molecular weight technique, it was found that the percentage of active cobalt depended on the Al/Co ratio. Subsequently, an equilibrium reaction was proposed to be Co + 2Al ? CoAl₂, where Co is cobalt(II) octanoate, Al is either of the aluminum alkyl‐activator species, and CoAl₂ is the active catalyst. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2256–2261, 2001     

Polymerization of isoprene with η5‐C5H4(tert‐Bu)TiCl3/MAO catalyst

cis‐Selective polymerizations of isoprene with the catalysts composed of η⁵‐C₅H₄(R)TiCl₃ (1; R?H, 2 ; tert‐Bu) and methylaluminoxane were investigated. Both catalysts showed remarkable catalytic activities for the polymerization of isoprene. The polymerization activities were strongly affected by the substituent introduced on cyclopentadienyl ring. Introduction of bulky tert‐butyl group was found to be effective for enhancement of polymerization activity, but the cis‐content of polyisoprene prepared by the 2 /MAO catalyst was lower than that by 1 /MAO catalyst. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1841–1844, 2004     

Investigation of catalyst‐transfer condensation polymerization for the synthesis of n‐type π‐conjugated polymer,poly(2‐dioxaalkylpyridine‐3,6‐diyl)

Kumada‐Tamao coupling polymerization of 6‐bromo‐3‐chloromagnesio‐2‐(3‐(2‐methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of boronic ester monomer 2 , which has the same substituted pyridine structure, with ^tBu₃PPd(o‐tolyl)Br were investigated for the synthesis of a well‐defined n‐type π‐conjugated polymer. We first carried out a model reaction of 2,5‐dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl₂ and then observed exclusive formation of 2,5‐diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada‐Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head‐to‐tail poly(pyridine‐2,5‐diyl), poly(3‐(2‐(2‐(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix‐assisted laser desorption ionization time‐of‐flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst‐transfer polymerization is accompanied with disproportionation. Suzuki‐Miyaura polymerization of 2 with ^tBu₃PPd(o‐tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl‐ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Bio‐safe synthesis of linear and branched PLLA

The catalytic activities of Bi(III) acetate (Bi(OAc)₃) and of creatinine towards the ring‐opening polymerization of L ‐lactide have been compared with those of a stannous (II) ethylhexanoate ((SnOct)₂)‐based system and with those of a system catalyzed by enzymes. All four were suitable catalysts for the synthesis of high and moderate molecular weight poly(L ‐lactide)s and the differences in reactivity and efficiency have been studied. Linear and branched poly(L ‐lactide)s were synthesized using these bio‐safe initiators together with ethylene glycol, pentaerythritol, and myoinositol as coinitiators. The polymerizations were performed in bulk at 120 and 140 °C and different reactivities and molecular weights were achieved by adding different amounts of coinitiators. A molecular weight of 105,900 g/mol was achieved with 99% conversion in 5 h at 120 °C with a Bi(OAc)₃‐based system. This system was comparable to Sn(Oct)₂ at 140 °C. The reactivity of creatinine is lower than that of Bi(OAc)₃ but higher compared with enzymes lipase PS (Pseudomonas fluorescens). A ratio of Sn(Oct)₂M_o/I_o 10,000:1 was needed to achieve a polymer with a reasonable low amount of tin residue in the precipitated polymer, and a system catalyzed by creatinine at 140 °C has a higher conversion rate than such a system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1214–1219, 2010     

Phenothiazine‐S,S‐dioxide‐ and fluorene‐based light‐emitting polymers: Introduction of e−‐deficient S,S‐dioxide into e−‐rich phenothiazine

A novel series of poly(10‐hexyl‐phenothiazine‐S,S‐dioxide‐3,7‐diyl) and poly(9,9′‐dioctyl‐fluorene‐2,7‐diyl‐alt‐10‐hexyl‐3,7‐phenothiazine‐S,S‐dioxide) (PFPTZ‐SS) compounds were synthesized through Ni(0)‐mediated Yamamoto polymerization and Pd(II)‐catalyzed Suzuki polymerization. The synthesized polymers were characterized by ¹H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ‐SS compounds were highly fluorescent with bright blue emissions in the solid state. Light‐emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish‐blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine‐S,S‐dioxide property, triggered by the introduction of an electron‐deficient SO₂ unit into the electron‐rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ‐SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236–1246, 2007     

Polymerization of (E)‐1,3‐Pentadiene and (E)‐2‐methyl‐1,3‐pentadiene with neodymium catalysts: Examination of the factors that affect the stereoselectivity

(E)‐1,3‐Pentadiene (EP) and (E)‐2‐methyl‐1,3‐pentadiene (2MP) were polymerized to cis‐1,4 polymers with homogeneous and heterogeneous neodymium catalysts to examine the influence of the physical state of the catalyst on the polymerization stereoselectivity. Data on the polymerization of (E)‐1,3‐hexadiene (EH) are also reported. EP and EH gave cis‐1,4 isotactic polymers both with the homogeneous and with the heterogeneous system, whereas 2MP gave an isotactic cis‐1,4 polymer with the heterogeneous catalyst and a syndiotactic cis‐1,4 polymer, never reported earlier, with the homogeneous one. For comparison, the results obtained with the soluble CpTiCl₃‐based catalyst (Cp = cyclopentadienyl), which gives cis‐1,4 isotactic poly(2MP), are examined. A tentative interpretation is given for the mechanism of the formation of the stereoregular polymers obtained and a complete NMR characterization of the cis‐1,4‐syndiotactic poly(2MP) is reported. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3227–3232