Polymerization Of Propylene Oxide Research Articles

Structure of poly(propylene oxide) obtained in the presence of K −, K +(15-crown-5) 2

Potassium isopropoxide and potassium tetraethylene glycoxide vinyl ether as well as small amounts of dipotassium tri- and tetraethylene glycoxides are formed in the initiation step of propylene oxide polymerization by K −, K +(15-crown-5) 2. Chain transfer reactions occur during the polymerization. Therefore, macromolecules with various starting groups, i.e. with the isopropyl, vinyl, allyl, and propenyl ones, are obtained in the process. The kind of end groups generally depends on the quenching agent used for termination. However, the macromolecules terminated in the chain transfer reactions possess exclusively the hydroxyl end group. The functionality of protonated polymers is equal to about 1.2 as a result of propagation occurring on dipotassium glycoxides.

Polymerization of methyl methacrylate and other polar monomers with alkylaluminum initiators bearing bidentate and tridentate N‐ and O‐donor ligands

AbstractDimethylaluminum complexes bearing bidentate amidate, oxypyridine, and salicylaldimine N,O‐ligands and tridentate N,N′,N″‐pyridyliminoamide ligands were synthesized and spectroscopically characterized. The complexes were investigated in both neutral and borane‐activated cationic forms, along with bidentate N,N′‐ligated aluminum amidinates, as catalysts for the polymerization of methyl methacrylate, ϵ‐caprolactone, and propylene oxide. The neutral complexes generally did not carry out polymerization, but the polymerization/oligomerization of all three monomers was achieved when the various catalysts were activated with B(C6F5)3 or [Ph3C]+[B(C6F5)4]−. The N,O‐ligated cations were much less active for polymerization than the analogous, more stable N,N′‐ligated amidinate cations; both types of cationic complexes catalyzed the ring‐opening cationic polymerization of tetrahydrofuran. B(C6F5)3 and [Ph3C]+[B(C6F5)4]− also independently carried out the oligomerization of propylene oxide. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1633–1651, 2002

Anionic ring-opening polymerization of propylene oxide in the presence of phosphonium catalysts

Anionic ring-opening polymerization of propylene oxide in the presence of potassium alcoholate initiator was accelerated by addition of the bulky phosphonium salt tetrakis[cyclohexyl(methyl)amino]phosphonium-tetrafluoroborate. Dipropylene glycol (DPG) was partially deprotonated (5%) and used as an initiator for the polymerization performed at 100 °C at normal pressure. The delocalization of the positive charge over five atoms promoted the formation of a separated ion pair, thus enhancing nucleophilicity and reactivity. Compared with those of polyaminophosphazenes and tetrabutylphosphonium cation, the average propagation rates increased in the order of Bu4P+, K+, P, P, and tBuP4H+. DPn for the polymers was in the range of 20–64. Characterization of poly(propylene oxide)s by means of 1H NMR, size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) showed low polydispersities (Mw/Mn) without any byproducts or impurities. The Mw/Mn obtained was 1.03–1.09 (MALDI-TOF-MS) and 1.11–1.15 (SEC), respectively. Values calculated from titration of the hydroxyl groups showed good agreement. Determination of the total degree of unsaturation in the range of 13–60 mmol/kg indicated larger amounts with increasing polymerization rates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 864–873, 2002; DOI 10.1002/pola.10163

Controlled ring‐opening polymerization of propylene oxide catalyzed by double metal‐cyanide complex

AbstractA double metal‐cyanide catalyst based on Zn3[Co(CN)6]2 was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. 13C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002

Anionic ring‐opening polymerization of propylene oxide in the presence of phosphonium catalysts

AbstractAnionic ring‐opening polymerization of propylene oxide in the presence of potassium alcoholate initiator was accelerated by addition of the bulky phosphonium salt tetrakis[cyclohexyl(methyl)amino]phosphonium‐tetrafluoroborate. Dipropylene glycol (DPG) was partially deprotonated (5%) and used as an initiator for the polymerization performed at 100 °C at normal pressure. The delocalization of the positive charge over five atoms promoted the formation of a separated ion pair, thus enhancing nucleophilicity and reactivity. Compared with those of polyaminophosphazenes and tetrabutylphosphonium cation, the average propagation rates increased in the order of Bu4P+, K+, P, P, and tBuP4H+. DPn for the polymers was in the range of 20–64. Characterization of poly(propylene oxide)s by means of 1H NMR, size exclusion chromatography (SEC), and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) showed low polydispersities (Mw/Mn) without any byproducts or impurities. The Mw/Mn obtained was 1.03–1.09 (MALDI‐TOF‐MS) and 1.11–1.15 (SEC), respectively. Values calculated from titration of the hydroxyl groups showed good agreement. Determination of the total degree of unsaturation in the range of 13–60 mmol/kg indicated larger amounts with increasing polymerization rates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 864–873, 2002; DOI 10.1002/pola.10163

NMR Assignments of Regioregular Poly(propylene oxide) at the Triad and Tetrad Level

Regioregular poly(propylene oxide), PPO, formed by simple base (KOH) and coordinate base (TPP)AlCl, (tetraphenylporphinato)aluminum chloride, ring-opening polymerization of propylene oxide, PO, has been studied by high field 13C{1H} NMR spectroscopy at various concentrations in CDCl3 and C6D6. The original assignments of Tonelli and Schilling [Macromolecules 1986, 19, 1337−1343] at the triad and diad sensitivity level have been extended to tetrad sensitivity.

A Comparative Study in the Ring-Opening Polymerization of Lactides and Propylene Oxide

The aluminum chloride complexes [(O∼∼O)AlCl]2, I, [(O∼CHMe∼O)AlCl]2, II, and TPPAlCl, III, where O∼∼O = 5,5‘,6,6‘-tetramethyl-3,3‘-di-tert-butyl-1,1‘-biphenoxide, O∼CHMe∼O = 2,2‘-ethylidenebis-4,6-di-tert-butylphenoxide, and TPP = tetraphenyl porphyrin, are shown to be inactive in initiating the ring-opening polymerization, ROP, of lactides, LA (L and rac). Upon addition of propylene oxide, PO, they lead to block oligomers/polymers of the form (PPO)n(PLA)m. The Union Carbide catalyst system known as calcium amide−alkoxide, [Ca(NH2)(OiPr)], is active in ROP of lactides at room temperature as well as PO. Block copolymers of PO and LA can be formed by the initial ROP of PO followed by the addition of LA but not from reactions involving the reverse order of the addition of PO/LA. The alkoxide aluminum compounds [(O∼CHMe∼O)Al(μ-OiPr)]2, IV, and TPPAlOMe, V, are active in PO polymerization at room temperature but will effect lactide ROP only upon heating to 80 °C. The stereoselectivity exhibited in ROP of PO by III and V and the Union Carbide catalyst system is not observed for ROP of rac-LA. These results are discussed in terms of the intimate mechanism of ring opening of PO and lactides, where it is proposed that coordinate catalysts differ in their operation. Single-site catalysis is favored for lactides but coordinate base catalysis for ROP of PO requires the cooperation of two metal sites. Copolymers of PO and LA are thus prepared as block copolymers by consecutive reactions. The copolymers have been characterized by 1H, 13C NMR spectroscopy, by mass spectrometry (GPC/ESI/MS and LD/FTMS), and by gel permeation chromatography.

Reactivity and derivatization of five-coordinate, chelated aluminum.

The convenient five-coordinate starting materials, Salen((t)Bu)AlCl (Salen((t)Bu) = N,N'-alkylene (or arylene) bis (3,5-di-tert-butyl-2-hydroxybenzylideneamine) (1-4) can be used in a wide range of reactions to form five-coordinate aluminum compounds. Herein, these reagents were used to produce new five-coordinate azides, LAlN(3) (L = Salen((t)Bu) (5), Salpen((t)Bu) (6), and Salomphen((t)Bu) (7)) through trimethylsilylhalide elimination. The decomposition of the azides produce first hydroxide (LAlOH (L = Salen((t)Bu) (8)) and, subsequently in the presence of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe(3) (L = Salen((t)Bu) (9), Salpen((t)Bu) (10), and Salomphen((t)Bu) (11)). Alkane elimination reactions may also be used to access this type of compound as evidenced by the formation of Salomphen((t)Bu)AlOSiPh(3) (12). Additionally, the first structurally characterized five-coordinate monomeric amide, Salcen((t)Bu)AlN(SiMe(3))(2) (13), can prepared by a salt elimination utilizing Salcen((t)Bu)AlCl (4). The compounds were characterized by spectroscopic methods ((1)H and (27)Al NMR, MS, and IR) and, in the case of 2 (Salpen((t)Bu)AlCl), 3 (Salomphen((t)Bu)AlCl) 9, 11, 12, and 13, by X-ray analysis. Several of the compounds were explored as potential catalysts for the living polymerization of propylene oxide.

Cationic aluminum alkyl complexes incorporating aminotroponiminate ligands.

The synthesis, structures, and reactivity of cationic aluminum complexes containing the N,N'-diisopropylaminotroponiminate ligand ((i)Pr(2)-ATI(-)) are described. The reaction of ((i)Pr(2)-ATI)AlR(2) (1a-e,g,h; R = H (a), Me (b), Et (c), Pr (d), (i)Bu (e), Cy (g), CH(2)Ph (h)) with [Ph(3)C][B(C(6)F(5))(4)] yields ((i)()Pr(2)-ATI)AlR(+) species whose fate depends on the properties of the R ligand. 1a and 1b react with 0.5 equiv of [Ph(3)C][B(C(6)F(5))(4)] to produce dinuclear monocationic complexes [([(i)Pr(2)-ATI] AlR)(2)(mu-R)][(C(6)F(5))(4)] (2a,b). The cation of 2b contains two ((i)()Pr(2)-ATI)AlMe(+) units linked by an almost linear Al-Me-Al bridge; 2a is presumed to have an analogous structure. 2b does not react further with [Ph(3)C][B(C(6)F(5))(4)]. However, 1a reacts with 1 equiv of [Ph(3)C][B(C(6)F(5))(4)] to afford ((i Pr(2)-ATI)Al(C(6)F(5))(mu-H)(2)B(C(6)F(5))(2) (3) and other products, presumably via C(6)F(5)(-) transfer and ligand redistribution of a [((i)()Pr(2)-ATI)AlH][(C(6)F(5))(4)] intermediate. 1c-e react with 1 equiv of [Ph(3)C][B(C(6)F(5))(4)] to yield stable base-free [((i)Pr(2)-ATI)AlR][B(C(6)F(5))(4)] complexes (4c-e). 4c crystallizes from chlorobenzene as 4c(ClPh).0.5PhCl, which has been characterized by X-ray crystallography. In the solid state the PhCl ligand of 4c(ClPh) is coordinated by a dative PhCl-Al bond and an ATI/Ph pi-stacking interaction. 1g,h react with [Ph(3)C][B(C(6)F(5))(4)] to yield ((i)Pr(2)-ATI)Al(R)(C(6)F(5)) (5g,h) via C(6)F(5)(-) transfer of [((i)Pr(2)-ATI)AlR][(BC(6)F(5))(4)] intermediates. 1c,h react with B(C(6)F(5))(3) to yield ((i)Pr(2)-ATI)Al(R)(C(6)F(5)) (5c,h) via C(6)F(5)(-) transfer of [((i)Pr(2)-ATI)AlR][RB(C(6)F(5))(3)] intermediates. The reaction of 4c-e with MeCN or acetone yields [((i)Pr(2)-ATI)Al(R)(L)][B(C(6)F(5))(4)] adducts (L = MeCN (8c-e), acetone (9c-e)), which undergo associative intermolecular L exchange. 9c-e undergo slow beta-H transfer to afford the dinuclear dicationic alkoxide complex [(((i)Pr(2)-ATI)Al(mu-O(i)()Pr))(2)][B(C(6)F(5))(4)](2) (10) and the corresponding olefin. 4c-e catalyze the head-to-tail dimerization of tert-butyl acetylene by an insertion/sigma-bond metathesis mechanism involving [((i)Pr(2)-ATI)Al(C=C(t)Bu)][B(C(6)F(5))(4)] (13) and [((i)Pr(2)-ATI)Al(CH=C((t)()Bu)C=C(t)Bu)][B(C(6)F(5))(4)] (14) intermediates. 13 crystallizes as the dinuclear dicationic complex [([(i Pr(2)-ATI]Al(mu-C=C(t)Bu))(2)][B(C(6)F(5))(4)](2).5PhCl from chlorobenzene. 4e catalyzes the polymerization of propylene oxide and 2a catalyzes the polymerization of methyl methacrylate. 4c,e react with ethylene-d(4) by beta-H transfer to yield [((i)Pr(2)-ATI)AlCD(2)CD(2)H][B(C(6)F(5))(4)] initially. Polyethylene is also produced in these reactions by an unidentified active species.

Anionic synthesis of well-defined, poly[(styrene)-block-(propylene oxide)] block copolymers

Well-defined, narrow molecular weight distribution (Mw/Mn ≤ 1.1) poly[(styrene)-block-(propylene oxide)] block copolymers with relatively high molecular weight poly(propylene oxide) blocks [e. g. Mn (PPO) = 10 000–12 000 g/mol] have been prepared by anionic polymerization. The polystyrene block (Mn = 5 000; Mw/Mn = 1.1) was prepared by alkyllithium-initiated polymerization of styrene followed by chain-end functionalization with ethylene oxide and protonation with acidic methanol. The resulting ω-hydroxyl-functionalized polystyrene was converted to the corresponding alkali metal salts with alkali metals (Na/K alloy, Rb, Cs) and then used to initiate block polymerization of propylene oxide in tetrahydrofuran. The effects of crown ethers (18-crown-6 and dicyclohexano-24-crown-8) and added dimethylsulfoxide were investigated. Chain transfer to the monomer resulted in significant amounts of poly(propylene oxide) formation (50%); however, the diblock molecular weight distributions were narrow. The highest molecular weight poly(propylene oxide) blocks (12 200 g/mol) were obtained in tetrahydrofuran with cesium as counterion without additives.

Immortal polymerization of propylene oxide: application to the synthesis of macrocycle precursors

Macromolecular SymposiaVolume 153, Issue 1 p. 17-25 Article Immortal polymerization of propylene oxide: application to the synthesis of macrocycle precursors Fabienne Nuytens, Fabienne NuytensSearch for more papers by this authorGarance Lopitaux, Garance LopitauxSearch for more papers by this authorCatherine Faven, Catherine FavenSearch for more papers by this authorXavier Coqueret, Xavier CoqueretSearch for more papers by this author Fabienne Nuytens, Fabienne NuytensSearch for more papers by this authorGarance Lopitaux, Garance LopitauxSearch for more papers by this authorCatherine Faven, Catherine FavenSearch for more papers by this authorXavier Coqueret, Xavier CoqueretSearch for more papers by this author First published: 21 December 2000 https://doi.org/10.1002/1521-3900(200003)153:1<17::AID-MASY17>3.0.CO;2-PCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume153, Issue1March 2000Pages 17-25 RelatedInformation

Bimetallic and cationic aluminum with N 3O 2 chelate ligands

The ligands aminobis( N-ethylenesalicylidenimine) (SalenN 3H 3) and aminobis( N-propylenesalicylidenimine) (SalpenN 3H 3) were used to form the bimetallic complexes SalenN 3H{AlMe 2} 2 ( 1), SalpenN 3H{AlMe 2} 2 ( 2), SalenN 3H{AlMeCl} 2 ( 3) and SalpenN 3H{AlMeCl} ( 4). When extracted in THF 3 and 4 redistribute to form the ionic compounds [SalenN 3H{Al(THF)}] + [AlMe 2Cl 2] − ( 5) and [SalpenN 3H{Al(THF)}] + [AlMe 2Cl 2] − ( 6). The compounds were characterized by Mp analyses, 1H-NMR and IR, and in the case of 2 and 6 by X-ray crystallography. Additionally, the potential of 5 and 6 to serve as propylene oxide polymerization catalysts was examined.

Aluminium and rare earths alkoxides as initiators for the heterogeneous anionic coordinated polymerisation of propylene oxide. A1H NMR approach of the regioselectivity and transfer ability of the catalytic system

In order to outline the placement of the monomer units during the heterogeneous anionic coordinated polymerization of propylene oxide, the regioselectivity of the first monomer insertion at the initiator was examined by 1 H NMR. To start, aluminium benzyl oxide chemically grafted onto a porous support was used as initiator. It was shown that the regioselectivity of the first insertion reflects the placement of the monomer units in the chain. Although there is no direct correlation between these two parameters, a knowledge of the regioselectivity of this first insertion allowed us to compare different catalytic systems. With aluminium alkoxides as initiators, both carbon atoms are attacked at random in the first insertion step. Adding triethylamine increases notably the regioselectivity. The replacement of aluminium by zirconium or a rare earth element gives about the same percentage of regular insertion as that obtained with the complex aluminium alkoxide-NEt 3 . On the other hand, the allyl double bond content was measured and the values of the transfer constant were deduced. Adding triethylamine to aluminium alkoxides or using Zr and rare earth based systems causes a decrease of the transfer constant. The more regular the PO insertion is, the lower is the transfer constant.

Aluminium and rare earths alkoxides as initiators for the heterogeneous anionic coordinated polymerisation of propylene oxide. A 1H NMR approach of the regioselectivity and transfer ability of the catalytic system

In order to outline the placement of the monomer units during the heterogeneous anionic coordinated polymerization of propylene oxide, the regioselectivity of the first monomer insertion at the initiator was examined by 1H NMR. To start, aluminium benzyl oxide chemically grafted onto a porous support was used as initiator. It was shown that the regioselectivity of the first insertion reflects the placement of the monomer units in the chain. Although there is no direct correlation between these two parameters, a knowledge of the regioselectivity of this first insertion allowed us to compare different catalytic systems. With aluminium alkoxides as initiators, both carbon atoms are attacked at random in the first insertion step. Adding triethylamine increases notably the regioselectivity. The replacement of aluminium by zirconium or a rare earth element gives about the same percentage of regular insertion as that obtained with the complex aluminium alkoxide-NEt3. On the other hand, the allyl double bond content was measured and the values of the transfer constant were deduced. Adding triethylamine to aluminium alkoxides or using Zr and rare earth based systems causes a decrease of the transfer constant. The more regular the PO insertion is, the lower is the transfer constant.

Polymerization of propylene oxide by a new neodymium complex of calixarene derivative

Polymerization of propylene oxide was performed in good yield and a high isotactic content of 58.0–70.6% by calixarene–neodymium complex 2/Al( i-Bu) 3/H 2O catalyst system under the following conditions: [PO]=4 mol/l ; [PO]/[Al]=300; Al/Nd=6–16; temperature, 70°C; reaction time, 22 or 46 h and solvent, toluene.

Neutral and Cationic Tetracoordinated Aluminum Complexes Featuring Tridentate Nitrogen Donors: Synthesis, Structure, and Catalytic Activity for the Ring-Opening Polymerization of Propylene Oxide and (d,l)-Lactide

The dilithium salts of N,N‘,N‘‘-tris(trimethylsilyl)diethylenetriamine (1), N-methyl-N‘,N‘‘-bis(trimethylsilyl)diethylenetriamine (2), and N-methyl-N‘,N‘‘-bis(diisopropyl)diethylenetriamine (3) reacted in THF, at −40 °C, with AlCl3 affording monomeric aluminum chloride derivatives 4 (55% yield), 5 (76% yield), and 6 (71% yield), respectively. Addition of 1 equiv of AlMe3 to the amine 2 gave rise to the five-coordinate dimethylaluminum derivative 9 (67% yield); heating a toluene solution of 9 overnight at 80 °C induces a loss of methane giving rise to the four-coordinate methylaluminum compound 10 (50% yield). The amine 2 also reacted at low temperature with LiAlH4 affording derivative 11 (38% yield). Compounds 4−6 reacted subsequently in toluene with 1 equiv of HCl and 1 equiv of AlCl3 to afford the first chiral tetracoordinated aluminum cations 12 (94% yield), 13 (93% yield), and 14 (90% yield), respectively. Single-crystal X-ray diffraction studies of derivatives 4, 5, 8, 10, 11, 12, and 15 have been carried out. They revealed that the tridentate nitrogen donors enforce an approximately trigonal-monopyramidal coordination geometry for neutral and cationic four-coordinate aluminum complexes. All cationic aluminum derivatives 12−14 and the neutral aluminum chloride 4 brought about the oligomerization of propylene oxide (PO). Low molecular weight polymers having narrow molecular weight distributions were obtained. The 13C NMR spectra of these polymers indicate that they consist exclusively of head-to-tail linkages and that these macromolecules are rich in meso diad and isotactic triad sequences. Due to the presence of a free axial site, a new mechanism for PO polymerization is proposed. Methyl- and hydridoaluminum derivatives 10 and 11, as well as aluminum alkoxide, prepared in situ by reacting derivative 13 with PO, initiated the polymerization of (d,l)-lactide in benzene at 80 °C. High molecular weight polymers of broad molecular weight distributions were obtained in good yields.

Effect of Cyclization on the Association Behavior of Block Copolymers in Aqueous Solution. Comparison of Oxyethylene/Oxypropylene Block Copolymers Cyclo-P34E104 and E52P34E52

Triblock copolymer E52P34E52 was prepared by sequential anionic polymerization of propylene oxide followed by ethylene oxide. Some of this copolymer was cyclized via acetal closure to yield a cyclic diblock copolymer, cyclo-P34E104, which was characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. Light scattering methods were used to study the micellization and micellar properties of the two copolymers: dynamic light scattering for hydrodynamic properties of the micelles, static light scattering for micellar molar mass and critical micellization conditions. The gelation of concentrated solutions was also studied. The critical micelle concentrations (cmc) of the two copolymers were similar for solutions at 40−50 °C, but the temperature dependence of the cmc was smaller for the linear copolymer. The cyclic copolymer in solution at 50−55 °C formed micelles with larger association numbers and hard-sphere volumes than its linear triblock counterpart.

Epoxide Polymerization and Copolymerization with Carbon Dioxide Using Diethylaluminum Chloride-25,27-Dimethoxy-26,28-dihydroxy-p-tert-butyl-Calix[4]arene System as a New Homogeneous Catalyst

ABSTRACT Previously unknown substituted chelate phenolatoaluminum chloride, (25,27-dimethoxy-p-tert-butylcalix[4]arene-26,28-diolato) aluminum chloride, was derived from the reaction of diethyl-aluminum chloride and 25,27-dimethoxy-26,28-dihydroxy-p-tert-butylcalix[4]arene at reactants 1:1 mole ratio. It was applied successfully for the polymerization of propylene oxide and cyclohexene oxide, and their copolymerization with carbon dioxide, leading to respective oligomers and co-oligomers. The catalyst structure and the structure of the obtained low-molecular-weight polymers and copolymers were studied using NMR spectroscopy. Poly(propylene oxide) obtained in the presence of the studied catalyst appeared to contain isotactic diads predominantly, whereas the obtained poly(cyclohexene oxide) did not exhibit any significantly prevailing sequences of either isotactic nor syndiotactic diads. The polymerization mechanism has been proposed and discussed in view of the obtained results.

Influence of the kind of crown ether on the heterogeneous polymerization of propylene oxide in the presence of potassium hydride

The influence of 12-crown-4, 15-crown-5, 18-crown-6, dicyclohexano-18-crown-6 and dicyclo-hexano-24-crown-8 on the propylene oxide polymerization with potassium hydride was studied. The highest reaction rate was obtained in the presence of 18-crown-6 or dicyclohexano-18-crown-6. The use of dicyclohexano-18-crown-6 was found to enhance the molecular mass of polymers more than other ligands. The observed effects were related to the heterogeneity of the reaction mixture and the structure of the crown ether complexes with the potassium cation.

Influence of the kind of crown ether on the heterogeneous polymerization of propylene oxide in the presence of potassium hydride

Influence of the kind of crown ether on the heterogeneous polymerization of propylene oxide in the presence of potassium hydride