Cationic ring-opening polymerization of 2-phenyl-1,2-oxaphospholane (deoxophostone)

Summary The ring-opening polymerization of deoxophostone 5, a five-membered cyclic phosphinite, has been studied. Some cationic initiators gave polymer whereas anionic and radical initiators as well as metal chloride (Lewis acid) catalysts did not yield polymer. The polymer consisted of a phosphine oxide repeating unit 6. The polymerization proceeded via the Arbuzov-type reaction. The reduction of polymer 6 with a HSiCl₃/Et₃N system gave polyphosphine 7.     

Cationic polymerization of selected α- and β-substituted vinyl ethers

Summary The cationic polymerization of various α- and β-substituted vinyl ethers, initiated by 1-iodo-1-(2-methylpropyloxy)ethane 1 and tetrabuty lammonium perchlorate (TBAP) was investigated. The polymerization of 2,3-dihydrofuran (DHF, 3a) in CH₂Cl₂ at -40°C proceeds via opening of the ethylenic double bond and yields polymers with narrow molar mass distributions and high glass transitions. The number average of molar mass increased linearly with conversion. Under these conditions, a controlled polymerization of two propenyl ethers (1-ethoxypropene 2a and 2-methoxypropene 2b) and two other cyclic unsaturated ethers (3,4-dihydro-2H-pyran 3b and 5-methyl-2,3-dihydrofuran 3c) could not be achieved. Either transfer reactions or the decomposition of 1 prevented the formation of high molar mass polymers of these vinyl ethers.     

Synthesis of poly(ɛ-caprolactone-b-isobutylene) diblock copolymer and poly(ɛ-caprolactone-b-isobutylene-b-ɛ-caprolactone) triblock copolymer

Summary Poly(isobutylene-b-ɛ-caprolactone) diblock and poly(ɛ-caprolactone-b-isobutylene-b-ɛ-caprolactone) triblock copolymers have been prepared and characterized. The synthesis involved the living cationic polymerization of IB, followed by capping with 1,1-diphenylethylene or 1,1-p-ditolylethylene and end-quenching with 1-methoxy-1-trimethylsiloxy-2-methyl-propene to yield methoxycarbonyl functional PIB. Hydroxyl end-functional PIB polymers were quantitatively obtained by the subsequent reduction of methoxycarbonyl end-functional PIB with LiAlH₄. The structure of hydroxyl end-functional PIBs was confirmed by ¹H NMR and IR spectroscopy. Poly(ɛ-caprolactone-b-isobutylene) diblock copolymers and poly(ɛ-caprolactone-b-isobutylene-b-ɛ-caprolactone) triblock copolymers were synthesized by the living cationic ring-opening polymerization of ɛ-caprolactone with hydroxyl end-functional PIB as macroinitiator in the presence of HCl•Et₂O via the “activated monomer mechanism”. The block copolymers exhibited close to theoretical M_ns and narrow molecular weight distributions. Received: 30 January 2002/Revised version: 19 February 2002/ Accepted: 19 February 2002     

A new bifunctional initiator for the living polymerization of hexamethylcyclotrisiloxane

Summary A bifunctional living poly(dimethylsiloxane), poly(DMS), was synthesized through the anionic ring-opening polymerization of hexamethylcyclotrisiloxane(D₃) (3) with an initiator system consisting of dilithium salt(2) of bis (p-hydroxydimethylsilyl)phenyl ether(1) and N-methylpyrrolidine in THF solution. The subsequent end-capping reaction of the bifunctional living poly(DMS) with dimethylvinylchlorosilane(4) provided the uniform size poly(DMS) having vinylsilane group at the both chain ends(5).     

Alternating copolymerization of 5-oxazolones with electrophilic monomers via zwitterion intermediates

Summary 5-Oxazolone (1a) and 4-methyl-5-oxazolone (1b) were found to serve as a nucleophilic monomer (M_N) toward electrophilic monomers (M_E) like acrylamide (AM) and 2-hydroxyethyl acrylate (HEA). Copolymerizations between these M_N and M_E monomers took place without added initiator at room temperature and at110 °C to give solid polymers having alternating structures of 3 and 4. The molecular weight of these alternating copolymers is not high. The copolymerization mechanism is explained in terms of zwitterionic intermediates involving a proton-transfer step.     

Polycondensation of N-Chlorobenzoquinonimines

Summary Self-condensations of 4-chloroimino-2, 5-cyclohexadiene-1-one 1 (benzoquinone N-chloroimine), 2-tert-butyl-4-chloroimino-2, 5-cyclohexadiene-1-one 2, and 3-tert-butyl-4-chloroimino-2, 5-cyclohexadiene-1-one 3 in N-methylpyrrolidinone containing inorganic bases have been investigated. Monomer 1 gave polymers having inherent viscosities of 0.27–0.33 dLg^–1. Monomers 2 and 3 only gave oligomers. ¹H NMR spectra suggest that polymerization of 1 mainly occurs at C-2 and C-6 positions. A Michael-type addition mechanism, based on the high -effect nucleophilicity of =NCl, is proposed.     

Tailor made liquid crystalline networks exhibiting a chiral smectic C (S C * ) mesophase via living cationic copolymerization

Summary Living cationic copolymerization of (2S, 3S)-(+)-2-chloro-3-methylpentyl 4-(8-vinyloxyoctyloxy)biphenyl-4-carboxylate (15-8) with 2-vinyloxyethyloxy methacrylate (16-2) leads to reactive copolymers poly[(15-8)-co-(16-2)]X/Y (where X/Y is the mol ratio between the two monomers in the copolymer) containing methacryloyl side groups. The thermally crosslinked copolymers with X/Y=5/5 to 9/1 display an enantiotropic chiral smectic C (S _C ^* ) mesophase.This paper is part 28 in the series: Molecular engineering of liquid-crystalline polymers by living polymerization. Part 27: V. Percec, Q. Zheng: Polym. Bull., previous paper in the issue     

Sequence-regulated oligomers and polymers by living cationic polymerization

Summary A new trimer (3) and a tetramer (4) of vinyl ethers with controlled repeat unit sequences were prepared through the living cationic polymerization initiated with the hydrogen iodide/zinc iodide (HI/ZnI₂) system in toluene at 40°C; for example, 4 consisted of the following sequence, H−CH₂CH(OnBu)−CH₂CH[OCH₂CH₂CH(COOEt)₂]−CH₂CH(OCH₂CH₂OCOC₆H₅)−CH₂CH[OCH₂CH₂−OCOC(CH₃)=CH₂]−OCH₃, and is a new methacrylate-type macromonomer. The synthesis involved sequential and successive reactions of the corresponding four vinyl ethers (each equimolar to hydrogen iodide) with the HI/ZnI₂-generated living oligomeric growing species, starting from the quantitative addition of hydrogen iodide to n-butyl vinyl ether and subsequent activation of the resulting adduct with ZnI₂. The structure and molecular weights of these sequence-regulated vinyl ether oligomers were verified by ¹H NMR and thermospray mass spectroscopy.     

Syntheses of well-defined poly(siloxane)-b-poly(styrene) and poly(norbornene)-b-poly(styrene) block copolymers using functional alkoxyamines

Functional alkoxyamines, 1-[4-(4-lithiobutoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (2) and 1-[4-(2-vinyloxyethoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (3) were prepared, and well-defined poly(hexamethylcyclotrisiloxane)-b-poly(styrene)[poly(D₃)-b-poly(St)] and poly(norbornene)-b-poly(St) [poly(NBE)-b-poly(St)] were prepared using the alkoxyamines. The first step was preparation of poly(D₃) and poly(NBE) macroinitiators, which were obtained by the ring-opening anionic polymerization of D₃ using 2 as an initiator and the ring-opening metathesis polymerization of NBE using 3 as a chain transfer. The radical polymerization of St by the poly(D₃) and poly(NBE) macroinitiators proceeded in the ‘living’ fashion to give well-defined poly(D₃)-b-poly(St) and poly(NBE)-b-poly(St) block copolymers.     

Synthesis of comb-shaped copolymers by combination of reversible addition-fragmentation chain transfer polymerization and cationic ring-opening polymerization

Comb-shaped graft copolymers with poly(methyl acrylate) as a handle were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP) techniques in three steps. First, copolymers of poly(styrene-co-chloromethyl styrene), poly(St-co-CMS), were prepared by RAFT copolymerization of St and CMS using 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate (EPDTB) as RAFT agent. Second, the polymerization of MA using poly(St-co-CMS)-SC(S)Ph as macromolecular chain transfer agent produced block copolymer poly(St-co-CMS)-b-PMA. Third, cationic ring-opening polymerization of THF was performed using poly(St-co-CMS)-b-PMA/AgClO₄ as initiating system to produce comb-shaped copolymers. The structures of the poly(St-co-CMS), poly(St-co-CMS)-b-PMA and final comb-shaped copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography (GPC).     

Anionic ring-opening polymerization of 2-phenyl-1,3,4-oxadiazolin-5-one and conversion of the resulting polymer,N-benzamido-1-nylon,to N-amino-1-nylon

Summary The ring-opening polymerization of 2-phenyl-1,3,4-oxadiazolin-5-one (1) was carried out anionically both in bulk and in DMF solution at 140°C for 15 h in the presence of various initiators, such as alkaline metal salts of 1, alkaline metal fluorides and tertiary amines, leading to N-benzamido-l-nylon (2) having Mns up to 2,000. Hydrolysis of the pendant benzamido groups of the resulting polymer was successfully achieved in aqueous ethanol containing concentrated hydrochloric acid at 100°C to give N-amino-l-nylon (3). The original polymer dissolves easily in aliphatic and aromatic alcohols and polar aprotic solvents, whereas the hydrolyzed polymer is not soluble in these solvents but highly soluble in water. In dilute aqueous solutions, the latter polymer behaves as common polyelectrolytes with flexible backbone. Polymers 2 and 3 began to lose weight in air at around 200 and 170°C, respectively.     

Behavior of deoxophostones family as nucleophilic monomers in no-catalyst copolymerization

Summary Deoxophostone family(2-phenyl-1,2-oxaphospholane1a, 2-phenyl-1,2-oxaphosphorlane1b, and 2-phenyl-1,2-thiaphospholane1c) copolymerized with acrylic acid without catalyst to produce the corresponding copolymers. The polymerization proceeded via a cyclic acyloxyphosphorane to produce poly-(phosphine oxide — ester)3a(or3b) from1a(or1b) and poly(phosphine oxide — thiolester)3c from1c, respectively, with acrylic acid. It is of interest that the copolymer from1c with acrylic acid was not poly(phosphine sulfide — ester)4 but3c. The reactions of1a or1b with pyruvic acid or 1,3-propane sultone were also investigated.The present authors dedicate this paper to the late Mr. Ken Mizuno.     

Transformation of cationic polymerization of tetrahydrofuran into anionic block copolymerization of methyl methacrylate

Summary A new approach has been developed to transform the cationic polymerization of tetrahydrofuran (THF) into anionic block copolymerization of methyl methacrylate (MMA). Several telechelic polytetrahydrofurans with secondary amine end-groups (PTHF-NHR, where R = benzyl, n-butyl or phenyl) have been synthesized. The PTHF-NHR, where R is a phenyl group, can be almost completely metallated by sodium naphthalene to form the polymeric anion which will initiate quantitative polymerization of MMA to form a block copolymer, poly(MMA-b-THF-b-MMA), exhibiting thermoplastic elastomer properties of tensile strength 157kg/cm² and elongation 700%.     

Synthesis and characterization of biodegradable poly(ε-caprolactone)/poly(γ-benzyl <Emphasis Type="SmallCaps">l</Emphasis>-glutamate) block copolymer

A biodegradable poly(ε-caprolactone)/poly(γ-benzyl l-glutamate) (PCL-b-PBLG) block copolymer was synthesized by ring-opening polymerization of N-carboxy-γ-benzyl l-glutamate anhydride (BLG-NCA) with amine-terminated poly(ε-caprolactone) (PCL-NH₂) as a macroinitiator. The PCL-NH₂ was prepared by deprotection of a PCL-CH₂CH₂NHBoc, which was obtained by ring-opening polymerization of ε-caprolactone (ε-CL) initiated by Boc-aminoethanol (HOCH₂CH₂NHBoc) using stannous octanoate as catalyst under microwave irradiation. The structures of the block copolymers were determined by IR, ¹H NMR, and GPC measurements. The results prove that BLG-NCA can be initiated by PCL-NH₂ to produce PCL-b-PBLG block copolymers.     

Molecular engineering of liquid crystalline polymers by living polymerization

Summary This paper describes the synthesis and characterization of poly{3-[4-cyano-4-biphenyl)oxy]propyl vinyl ether} [poly(6-3)] macromonomers obtained by the functionalization of the growing chain end of the corresponding living polymer obtained by the initiation of the cationic polymerization of 3-[4-cyano-4-biphenyl)oxy]propyl vinyl ether with CF₃SO₃H/S(CH₃)₂, with 2-hydroxy ethyl methacrylate [poly(6-3)-I], 2-[2-(2-allyloxyethoxy)ethoxy]ethanol [poly(6-3)-II] and 10-undecen-1-ol [poly(6-3)-III].Part 20: V. Percec and M. Lee, J. Mater. Chem., submitted     

Living polymerization of isobutylene initiated byp-dicumyl chloride/BCl3/n-Bu4NX systems

Summary The 1,4-di-(2-chloro-2-propyl)-benzene (pDCC)/BCl₃/IB system was investigated in the presence and absence ofn-Bu₄NX. The presence ofn-Bu₄NX (X=Cl or I) changes the mechanism increasing the living character of the polymerization of isobutylene in both cases. Whenn-Bu₄NCl is added, BCl₄ ^– is formed and as a common ion in excess it shifts the dissociation equilibrium toward the non-dissociated species. In the case of the addition ofn-Bu₄NI, an exchange reaction between the gegenions, i.e., BCl₄ ^– and BCl₃I^– has been recognised and a possible reaction mechanism is given.     

Cationic ring-opening polymerization of 2-phenyl-1,3,6,2-trioxaphosphocane

Summary The ring-opening polymerization of 2-phenyl-1,3,-6,2-trioxaphosphocane (4), an eight-membered cyclic phosphonite, has been investigated. Cationic initiators of PhCH₂-Cl and MeOTf gave polymers, whereas anionic and radical initiators did not yield polymer. The structure of polymer was examined by IR, ¹H, ³¹P, and ³¹C NMR spectroscopy of polymers and elemental analysis as well as the alkaline hydrolysis products. The polymer consisted of two different units, i.e., the major part is the normal phosphinate structure 5 and the minor part is the isomerized unit 6 in 7% with PhCH₂Cl initiation and in 34% with MeOTf initiator. The difference in nature of propagating species from these two initiators are discussed in connection with their reactivities.On leave from the Institute of Chemistry, Academia Sinica, Beijing, China     

Syntheses of AB2 3- and AB4 5-miktoarm star copolymers by combination of the anionic ring-opening polymerization of hexamethylcyclotrisiloxane and nitroxide-mediated radical polymerization of styrene

AB₂ 3- and AB₄ 5-miktoarm star copolymers were prepared by combination of the anionic ring-opening polymerization (AROP) of hexamethylcyclotrisiloxane (D₃) and the TEMPO-mediated radical polymerization of styrene (St). Initially, two kinds of dendritic multifunctional initiators were prepared. One has a 4-bromobutoxy group and two TEMPO-based alkoxyamines and the other has a 4-bromobutoxy group and four TEMPO-based alkoxyamines. Treatment of the multifunctional initiators with tert-butyllithium gave the corresponding lithiobutoxy derivatives, and AROP of D₃ by the lithiobutoxy derivatives gave poly(D₃) with M_w/M_n of 1.07-1.12. Nitroxide-mediated radical polymerization of St by the poly(D₃)s at 120 °C gave AB₂ 3- and AB₄ 5-miktoarm star copolymers with M_w/M_n of 1.15-1.28. Their structures were analyzed by means of ¹H NMR and SEC measurements.     

Polyisobutylene-containing block polymers by sequential monomer addition

Novel poly(acenaphtylene-b-isobutylene-b-acenaphtylene) (PAc-PIB-PAc) triblock copolymers exhibiting thermoplastic elastomer (TPE) properties have been prepared. The synthesis involved the addition of acenaphtylene (Ac) to living polyisobutylene dications (PIB) obtained by living isobutylene (IB) polymerization induced by the dicumyl methyl ether (DiCumOMe)/TiCl₄ initiating system at-80°C. The triblocks contain very short polyacenaphtylene (PAc) blocks (M_n9,000) and consequently yield very soft, low modulus TPEs. Efforts to develop conditions for the living carbocationic polymerization (LCPzn) of Ac have failed.For Part VIII of this subseries see J. P. Kennedy, S. Midha, B. Keszler: Macromolecules (in press)     

Syntheses and characterizations of side-chain liquid crystalline poly(glycidyl ether)s with biphenyl mesogenic group

Summary Four three-armed poly(glycidyl ether)s with biphenyl mesogenic group and various lengths of spacer, new side-chain liquid crystalline polymers, were synthesized by cationic ring-opening polymerization of the corresponding monomers in the presence of 2,2-dihydroxymethylbutanol and BF₃·OEt₂ as initiator. The structures of the obtained poly(glycidyl ether)s were verified by ¹H and ¹³C NMR spectroscopy, and their liquid crystalline behaviors were studied by differential. scanning calorimetry (DSC and optical polarizing microscopy (OPM). Received: 5 January 1999/Revised version: 20 April 1999/Accepted: 26 April 1999