Cationic Polymerization Conditions Research Articles

Controlled Synthesis of Poly(vinyl ether)-Grafted Poly(phenylacetylene)s by a Combination of Living Coordination Polymerization and Living Cationic Polymerization.

We newly designed a functionalized monomer (PhAVE-AcOH) containing a phenylacetylene (PhA) group and a 1-(acetoxy)ethoxy group, the latter of which is expected to act as an initiator moiety in combination with Lewis acid-based activators under living cationic polymerization conditions. A polyPhA-based multifunctional initiator poly(PhAVE-AcOH) with a narrow molecular weight distribution (Mw/Mn = 1.02) was synthesized by Rh complex-mediated living coordination polymerization of PhAVE-AcOH. Then, living cationic graft polymerization of isobutyl vinyl ether (IBVE) was performed employing the pendant 1-(acetoxy) ethoxy initiating moiety of poly(PhAVE-AcOH) to form polyIBVE-grafted polyPhA(polyPhA-g-polyIBVE), where both the main chain and side chains possessed well-controlled structures (Mw/Mn = 1.05–1.10). We found that UV–vis absorption spectra of polyPhA-g-polyIBVE were progressively redshifted with increasing molecular weights of the graft chain.

Application of a carbazole derivative as a spectroscopic fluorescent probe for real time monitoring of cationic photopolymerization

Abstract The performance of 1-(9-ethylcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione (1) as a fluorescent probe for the monitoring of cationic photopolymerization processes by Fluorescence Probe Technique (FPT) has been evaluated in comparison with the response of 7-diethylamino-4-methylcoumarin (Coumarin 1) (2). Triethylene glycol divinyl ether and diphenyliodonium hexafluorophosphate were used as an example monomer and a cationic photoinitiator respectively. It has been found that the probe 1 withstands the cationic polymerization conditions and provides correct probe response. 1-(9-ethylcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione shifts its fluorescence spectrum with progress of cationic photopolymerization of the monomer, which enables the monitoring of the polymerization progress using the fluorescence intensity ratio measured at two different wavelengths as the progress indicator. By comparing the behavior of 1 and 2, it has been documented that the fluorescence spectrum of probe 1 shows a spectacular hypsochromic shift (Δλ = 33 nm) upon the monomer polymerization, while the shift of 2 is three times smaller (Δλ = 11 nm). Moreover, the sensitivity of probe 1 is more than 2.5-times higher than that of any other probes suitable for monitoring cationic polymerization processes, reported previously. Therefore, application of the carbazole derivative (1) as a new probe for the monitoring of the crosslinking process of coatings cured by cationic photopolymerization has been proposed.

Dynamic Covalent Macrocyclic Poly(phthalaldehyde)s: Scrambling Cyclic Homopolymer Mixtures Produces Multi-Block and Random Cyclic Copolymers

We recently reported the cationic polymerization of o-phthalaldehyde to macrocyclic poly(phthalaldehyde) polymers. Resubjecting the cyclic polymers to the polymerization conditions led to a redistribution of the polymer to a new cyclic structure consistent with thermodynamic equilibrium. We now report the synthesis of cyclic poly(phthalaldehyde) derivatives and demonstrate the scrambling of distinct homopolymer mixtures to copolymers under the cationic polymerization conditions. Homopolymer mixtures are found to rapidly redistribute, first to multiblock cyclic copolymers. With extended reaction time, random macrocyclic copolymers are obtained. Evolution of the microstructure was monitored by NMR spectroscopy, MALDI–TOF mass spectrometry, and gel permeation chromatography (GPC). The reported scrambling method leads to the rapid preparation of macrocyclic copolymers of high molecular weight with variable microstructure depending on reaction times and catalyst loadings.

α-Substituent Effect on o-Vinylbenzaldehyde Cyclopolymerization.

The cationic cyclopolymerization of o-vinylbenzaldehydes initiated by boron trifluoride is described. Unlike the incomplete conversion of o-vinylbenzaldehyde (1) at 0 °C, α-methyl-substituted monomers (2) and (3) undergo cyclopolymerizations with complete conversions at -78 °C. On the other hand, α-phenyl-substituted monomer (4) generated indenyl alcohol (7) when subjected to cationic polymerization conditions. The proposed mechanism for o-(α-methyl)vinylbenzaldehyde polymerization explains the importance of reaction temperature for polymer formation. Resulting amorphous poly(o-(α-methyl)vinylbenzaldehyde (10) exhibited good thermal stability (Tonset = 340 °C) with a Tg of 153 °C. Polymer (10) is a brittle and glassy plastic with a storage modulus (E') of 3 × 108 Pa and elongation at break of ∼3%.

The performance of 7‐hydroxycoumarin‐3‐carbonitrile and 7‐hydroxycoumarin‐3‐carboxylic acid as fluorescent probes for monitoring of cationic photopolymerization processes by FPT

AbstractThe applicability of 7‐hydroxycoumarin‐3‐carbonitrile (1) and 7‐hydroxycoumarin‐3‐carboxylic acid (2) as fluorescent probes for monitoring of cationic photopolymerization processes by fluorescence probe technique (FPT) was evaluated in comparison to the response of 7‐diethylamino‐4‐methylcoumarin (C1). Triethylene glycol divinyl ether and diphenyliodonium hexafluorophosphate were used as an example monomer and a cationic photoinitiator, respectively. It has been found that the probe 1 withstands the cationic polymerization conditions and provides correct probe response. The probes 2 and C1 undergo side reactions under the cationic polymerization conditions that make them unusable for monitoring of the polymerization progress at high monomer conversions. The application of 1 as an amine‐free probe for monitoring of curing progress of photocurable coatings cured by cationic photopolymerization is proposed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Aminophthalimide probes for monitoring of cationic photopolymerization by fluorescence probe technology and their effect on the polymerization kinetics

The performance of a series of phthalimide derivatives as fluorescent probes for monitoring of cationic photopolymerization of monomers by Fluorescence Probe Technology (FPT) has been studied in comparison to the performance of a 7-diethylamino-4-methylcoumarin (Coumarin 1) probe. It was found that the phthalimide probes are much more stable than Coumarin 1 under cationic polymerization conditions. Moreover, the aminophthalimide probes turned out to be long-wavelength sensitizers for the diaryliodonium photoinitiators used to initiate the polymerization process. The sensitizing effect of the probes compensates in excess the inhibiting effect of their amino groups on the cationic polymerization kinetics.

Living/controlled cationic cyclopolymerization of divinyl ether with a cyclic acetal moiety: Synthesis of poly(vinyl ether)s with high glass transition temperature based on incorporation of cyclized main chain and cyclic side chains

AbstractCationic cyclopolymerization of 2‐methyl‐5,5‐bis(vinyloxymethyl)‐1,3‐dioxane (1), a divinyl ether with a cyclic acetal group, was investigated with the HCl/ZnCl2 initiating system in toluene and methylene chloride at −30 °C. The reaction proceeded quantitatively to give gel‐free, soluble polymers in organic solvents. The number‐average molecular weight (Mn) of the polymers increased in direct proportion to monomer conversion, and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that the polymerization proceeded in living/controlled manner. The contents of the unreacted vinyl groups in the produced soluble polymers were less than ∼3 mol %, and therefore, the degree of cyclization was determined to be ∼97%. In contrast, the pendant cyclic acetal groups remained intact in the polymers under the present cationic polymerization conditions. These facts show that cyclopolymerization of 1 almost exclusively occurred and the poly(vinyl ether)s with the cyclized repeating units and cyclic pendant acetal rings were obtained. Glass transition temperature (Tg) and thermal decomposition temperature (Td) of poly(1) (Mn = 7870, Mw/Mn = 1.57) were found to be 166 and 338 °C, respectively, indicating that poly(1) had high Tg and high thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 952–958, 2010

Polymerization of vinyl compounds in the presence of perfluoroisopropenyl ester

AbstractTo report a new polymerization reaction phenomenon, this article examines the polymerization of butyl vinyl ether and N‐vinylcarbazole in the presence of 2‐benzoxypentafluoropropene [CF2C(CF3)OCOC6H5 or BPFP]. The homopolymer of butyl vinyl ether was produced in the presence of a catalytic amount of BPFP in high yields. N‐Vinylcarbazole, which is a monomer well‐known for producing its homopolymer under cationic polymerization conditions, also yielded its homopolymer in the presence of BPFP. It was concluded that some cationic species would be yielded by the addition of BPFP. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 908–910, 2007.

Direct synthesis of amphiphilic block copolymers from glycidyl methacrylate and poly(ethylene glycol) by cationic ring‐opening polymerization and supramolecular self‐assembly thereof

AbstractAmphiphilic block copolymers composed of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic poly(glycidyl methacrylate) (PGMA) block were synthesized through cationic ring‐opening polymerization with PEG as the precursor. The model reactions indicated that the reactivity of the epoxy groups was higher than that of the double bonds in the bifunctional monomer glycidyl methacrylate (GMA) under the cationic polymerization conditions. Through the control of the reaction time in the synthesis of block copolymer PEG‐b‐PGMA, a linear GMA block was obtained through the ring‐opening polymerization of epoxy groups, whereas the double bond in GMA remained unreacted. The results showed that the molecular weight of the PEG precursor had little influence on the grafting of GMA, and the PGMA blocks almost kept the same length, despite the difference of the PEG blocks. In addition, the PGMA blocks only consisted of several GMA units. The obtained amphiphilic PEG‐b‐PGMA block copolymers could form polymeric core–shell micelles by direct molecular self‐assembly in water. The crosslinking of the PGMA core of the PEG‐b‐PGMA micelles, induced by ultraviolet radiation and heat instead of crosslinking agents, greatly increased the stability of the micelles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2038–2047, 2005

Tetrafunctional initiators for cationic polymerization of olefins

Abstract3,3′,5,5′‐Tetrakis(2‐chloro‐2‐propyl)biphenyl (biphenyl tetracumyl chloride, BPTCC) and 1,3‐bis[3,5‐bis(2‐chloro‐2‐propyl)phenoxy]propane (diphenoxypropane tetracumyl chloride, DPPTCC) were synthesized as initiators for quasiliving cationic polymerization of isobutylene (IB). In the synthesis of BPTCC, tetrafunctionality was achieved via the coupling of dimethyl 5‐bromoisophthalate (DMBI) using nickel dibromide bis(triphenylphosphine) and zinc in the presence of a base; in the synthesis of DPPTCC, two equivalents of dimethyl 5‐hydroxyisophthalate were linked via reaction with 1,3‐dibromopropane in the presence of potassium carbonate. Both initiators were used to initiate the polymerization of IB under quasiliving cationic polymerization conditions. PIB initiated from BPTCC revealed a chain end/molecule value (as determined by 1H‐NMR) of 3.85, verifying the nearly exclusive production of 4‐arm polyisobutylene (PIB). GPC analysis revealed a narrow peak representing the target four‐arm PIB, with a slight shoulder at high elution volumes (low molecular weights). GPC analysis of the PIB initiated by DPPTCC revealed multimodal distributions, suggesting the formation of two‐, three‐, and four‐arm star polymers during the polymerization. This behavior was attributed to Friedel–Crafts alkylation of the initiator core after the addition of one IB unit, which was activated by the electron‐donating oxytrimethyleneoxy linking moiety. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5942–5953, 2004

Poly(styrene‐b‐isobutylene) multiarm star‐block copolymers

Multiarm star-branched polymers based on poly(styrene-b-isobutylene) (PS-PIB) block copolymer arms were synthesized under controlled/living cationic polymerization conditions using the 2-chloro-2-propylbenzene (CCl)/TiCl4/pyridine (Py) initiating system and divinylbenzene (DVB) as gel-core-forming comonomer. To optimize the timing of isobutylene (IB) addition to living PS⊕, the kinetics of styrene (St) polymerization at −80°C were measured in both 60 : 40 (v : v) methyl cyclohexane (MCHx) : MeCl and 60 : 40 hexane : MeCl cosolvents. For either cosolvent system, it was found that the polymerizations followed first-order kinetics with respect to the monomer and the number of actively growing chains remained invariant. The rate of polymerization was slower in MCHx : MeCl (kapp = 2.5 × 10−3 s−1) compared with hexane : MeCl (kapp = 5.6 × 10−3 s−1) ([CCl]o = [TiCl4]/15 = 3.64 × 10−3M; [Py] = 4 × 10−3M; [St]o = 0.35M). Intermolecular alkylation reactions were observed at [St]o = 0.93M but could be suppressed by avoiding very high St conversion and by setting [St]o ≤ 0.35M. For St polymerization, kapp = 1.1 × 10−3 s−1 ([CCl]o = [TiCl4]/15 = 1.82 × 10−3M; [Py] = 4 × 10−3M; [St]o = 0.35M); this was significantly higher than that observed for IB polymerization (kapp = 3.0 × 10−4 s−1; [CCl]o = [Py] = [TiCl4]/15 = 1.86 × 10−3M; [IB]o = 1.0M). Blocking efficiencies were higher in hexane : MeCl compared with MCHx : MeCl cosolvent system. Star formation was faster with PS-PIB arms compared with PIB homopolymer arms under similar conditions. Using [DVB] = 5.6 × 10−2M = 10 times chain end concentration, 92% of PS-PIB arms (Mn,PS = 2600 and Mn,PIB = 13,400 g/mol) were linked within 1 h at −80°C with negligible star–star coupling. It was difficult to achieve complete linking of all the arms prior to the onset of star–star coupling. Apparently, the presence of the St block allows the PS-PIB block copolymer arms to be incorporated into growing star polymers by an additional mechanism, namely, electrophilic aromatic substitution (EAS), which leads to increased rates of star formation and greater tendency toward star–star coupling. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1629–1641, 1999

Poly(styrene-b-isobutylene) multiarm star-block copolymers

Multiarm star-branched polymers based on poly(styrene-b-isobutylene) (PS-PIB) block copolymer arms were synthesized under controlled/living cationic polymerization conditions using the 2-chloro-2-propylbenzene (CCl)/TiCl4/pyridine (Py) initiating system and divinylbenzene (DVB) as gel-core-forming comonomer. To optimize the timing of isobutylene (IB) addition to living PS⊕, the kinetics of styrene (St) polymerization at −80°C were measured in both 60 : 40 (v : v) methyl cyclohexane (MCHx) : MeCl and 60 : 40 hexane : MeCl cosolvents. For either cosolvent system, it was found that the polymerizations followed first-order kinetics with respect to the monomer and the number of actively growing chains remained invariant. The rate of polymerization was slower in MCHx : MeCl (kapp = 2.5 × 10−3 s−1) compared with hexane : MeCl (kapp = 5.6 × 10−3 s−1) ([CCl]o = [TiCl4]/15 = 3.64 × 10−3M; [Py] = 4 × 10−3M; [St]o = 0.35M). Intermolecular alkylation reactions were observed at [St]o = 0.93M but could be suppressed by avoiding very high St conversion and by setting [St]o ≤ 0.35M. For St polymerization, kapp = 1.1 × 10−3 s−1 ([CCl]o = [TiCl4]/15 = 1.82 × 10−3M; [Py] = 4 × 10−3M; [St]o = 0.35M); this was significantly higher than that observed for IB polymerization (kapp = 3.0 × 10−4 s−1; [CCl]o = [Py] = [TiCl4]/15 = 1.86 × 10−3M; [IB]o = 1.0M). Blocking efficiencies were higher in hexane : MeCl compared with MCHx : MeCl cosolvent system. Star formation was faster with PS-PIB arms compared with PIB homopolymer arms under similar conditions. Using [DVB] = 5.6 × 10−2M = 10 times chain end concentration, 92% of PS-PIB arms (Mn,PS = 2600 and Mn,PIB = 13,400 g/mol) were linked within 1 h at −80°C with negligible star–star coupling. It was difficult to achieve complete linking of all the arms prior to the onset of star–star coupling. Apparently, the presence of the St block allows the PS-PIB block copolymer arms to be incorporated into growing star polymers by an additional mechanism, namely, electrophilic aromatic substitution (EAS), which leads to increased rates of star formation and greater tendency toward star–star coupling. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1629–1641, 1999

Selective cationic addition polymerization of 2,4-dimethylene-1,3-dioxolane by a common Lewis acid: synthesis of vinyl ether-pendant polymer under cationic polymerization conditions

Selective cationic addition polymerization of 2,4-dimethylene-1,3-dioxolane by a common Lewis acid: synthesis of vinyl ether-pendant polymer under cationic polymerization conditions

Polymerization of Aromatic Aldehydes. VII. Cyclopolymerization of o-FormylphenylacetaIdehyde and Formation of a Cyclic Trimer

Polymerization of o-formylphenylacetaldehyde was carried out with various catalysts. The polymer obtained below −60°C with BF3OEt2 catalyst was soluble in common organic solvents and was confirmed as a cyclopolymer composed of 6-membered cyclized units. The cationic cyclization step in the cyclopolymerization of o-formylphenylacetaldehyde was inferred to proceed through a intermediate or concerted scheme similar to those proposed for the cationic propagation of o-phthalalde-hyde.On the other hand, under cationic polymerization conditions over −40°C o-formylphenylacetaldehyde gave a cyclic trimer (mp 284–285°C) possessing fused ring ether, which had no aldehyde group. Interestingly, the cyclic trimer was also produced from the polymer by treatment with BF3OEt2 in methylene dichloride.Cyclopolymers of o-formylphenylacetaldehyde were also obtained with Ziegler catalyst at 0 and −78°C, and with t-BuOLi catalyst at −78°C.

New tin-containing unsaturated glycol ethers

1. New unsaturated diethers of glycols, which are derivatives of vinyl alcohol and 3-(triethyltin)propyn-3-ol-1, were obtained by the reaction of sodium-3-propynyloxyalkylvinyl ethers with triethylchlorotin. 2. The behavior of the synthesized vinyl ethers under electrophilic addition and cationic polymerization conditions was studied. The tinacetylenic fragment is split at the Sn- C≡ bond by electrophilic reagents, while practically completely suppressing the reactivity of the vinyloxy-group.