Anionic living polymerization of styrenes containing electron-withdrawing groups

Six styrene derivatives containing electron-withdrawing groups were synthesized and polymerized with anionic initiators in THF to afford stable anionic living polymers. The electron-withdrawing substituents are N,N-dialkylamide(1), N-alkylimino(2), oxazoline(3), tert-butyl ester(4), N,N-dialkylsulfonamide(5) and cyano(6) moieties. The polymers obtained have predictable molecular weights and narrow molecular weight distributions. The respective postpolymerizations proceeded with quantitative efficiency indicating that each polymer chain end retained the propagating reactivity. However, the resulting living polymers could not initiate the polymerizations of styrene and isoprene. On the other hand, the styrene derivatives(5 and 6) were polymerized with weak nucleophilic initiators, such as living polymer of tert-butyl methacrylate. These results suggest that the electron-withdrawing groups stabilize the living ends and also activate the respective monomers for anionic polymerization. The substitution effect reflects on the ¹³C NMR chemical shift of β-carbon of each vinyl group. The signal of the β-carbon appeared at lower magnetic field than that of styrene indicating electron deficiency on the carbon-carbon double bond of these monomers.     

Novel synthesis of photocrosslinkable polymers

A new preparative route to photocrosslinkable polymers in which the polymers are produced directly from the polymerization of vinyl monomers having photocrosslinkable groups has been investigated. The photosensitive resins thus produced have higher sensitivity and resolution than conventional photosensitive resins. The monomers were synthesized from the esterification of vinylphenols or vinyl β-chloroethyl ether with cinnamic acid, β-styrylacrylic acid, and their homologs, and from the etherification of vinyl β-chloroethyl ether with hydroxychalcones. Homopolymerizations of these monomers and their copolymerizations with other comonomers were investigated with the use of both radical and ionic initiators. It is shown that radical polymerization of the monomers gave soluble polymers only at low conversion. Anionic initiators did not initiate polymerization. Cationic polymerization imparted soluble polymers in high yield, except for the monomers bearing cyano groups, which generally gave insoluble polymers. Infrared and NMR spectroscopic investigation of the cationically obtained soluble polymers and comparative investigation by cationic polymerization of model compounds indicated that polymerization of the monomers proceeds through the vinyl double bond without affecting the photosensitive unsaturated bond. Thus, linear photocrosslinkable polymers with an intact photoreactive group may be produced by cationic polymerization. In general, these polymers have uniform structure and modifiable physical properties depending on the monomer used. The polymer thus obtained from β-vinyloxyethyl cinnamate has been shown to have excellent properties for use as a photo-resist.     

Vinyl monomers bearing chromophore moieties and their polymers. II. Fluorescence and initiation behavior of N-(4-N′, N′-dimethylaminophenyl)maleimide and its polymer

A maleimide bearing electron-donating chromophore, N-(4-N′,N′-dimethylaminophenyl)-maleimide (DMAPMI) was synthesized from N, N-dimethylaminoaniline and maleic anhydride in the presence of acetic anhydride and sodium acetate. DMAPMI can be easily copolymerized with vinyl acetate (VAc). In addition, it can be easily homopolymerized by UV light irradiation or by using AIBN or BPO as an initiator. The fluorescence spectra of DMAPMI and its polymer or copolymer were recorded and compared at the same chromophore concentrations. It was observed that the fluorescence emission intensity of DMAPMI was much lower than those of its polymers. This may be due to the occurrence of intermolecular charge transfer interaction between the electron-donating dimethylaminophenyl moiety and acrylic electron-accepting carbon-carbon double bond in the monomer. The model compound, N-(4-N′, N′-dimethylaminophenyl)succinimide (DMAPSI), which has no carbon-carbon double bond, displayed the same fluorescence behavior as DMAPMI polymers. The fluorescence of DMAPMI polymers and DMAPSI can be quenched by electron-deficient compounds such as AN, TCNE, MMA, etc. All these results supported the above conclusion. This is another example of the “fluorescence structural self-quenching effect” termed by us previously and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. Study of the initiation behavior of DMAPMI and its polymer showed that they could initiate the photopolymerization of AN, by combination with BPO, they could also initiate the thermopolymerization of vinyl monomers such as MMA. © 1996 John Wiley & Sons, Inc.     

Polymerization of allyl(vinyl phenyl) ethers and reactions of the resulting polymers

Solution polymerizations of allyl(o-vinyl phenyl)ether and allyl(p-vinyl phenyl)ether with cationic and radical initiators were investigated. Soluble polymers were formed in polymerizations with boron trifluoride etherate and with benzoyl peroxide. In polymerization with azobisisobutyronitrile the polymerization in dilute solution gave a soluble polymer, whereas that in concentrated solution gave a crosslinked, insoluble one. For informationon the polymerization behavior some infrared and ultraviolet spectroscopic investigations of the soluble polymers were made. From these results it appears that polymers with pendant allyl groups are formed in polymerization with boron trifluoride etherate at low temperature, and polymers containing pendant vinyl groups and allyl groups are obtained with the two types of radical initiator. Copolymerizations of these monomers with ethyl vinyl ether and styrene with the use of boron trifluoride etherate were sucessfully effected. Such reactions as Claisen rearrangement, crosslinking induced with radical initiators, and epoxidation with perbenzoic acid were examined for the polymers prepared in the polymerization with boron trifluoride etherate. Good results were obtained for the former two reactions. However, the latter was unsuccessful.     

Vinyl monomers bearing chromophore moieties and their polymers. V. Synthesis and fluorescence behavior of a vinyloxy monomer bearing electron-accepting chromophore moiety,N-(2-(vinyloxy)ethyl)-1,8-naphthalimide,and its polymer

A vinyloxy monomer bearing electron-accepting chromophore, N-(2-(vinyloxy)ethyl)-1,8-naphthalimide (VOENI), was synthesized by reaction of potassium 1,8-naphthalimide with 2-chloroethyl vinyl ether. VOENI can be homopolymerized by cationic initiation and copolymerized with maleic anhydride (MAn) under radical initiation. The fluorescence behaviors of VOENI and its polymers were investigated. It has been found that the fluorescence intensity of the VOENI monomer is much lower than that of its polymers at the same chromophore concentration. This means that a “structural self-quenching effect” (SSQE) has been also observed in the vinyloxy monomer consisting of an electron-accepting chromophore, which has opposite electronic structure in comparison with acrylates bearing electron-donating chromophores as we have reported previously. The SSQE is attributed to the charge-transfer interaction between the electron-accepting chromophore and the electron-donating double bond in the same molecule. The fluorescence quenching of 1,8-naphthalic anhydride and P(VOENI-co-MAn) by ethyl vinyl ether (EVE), dihydrofuran, triethylamine (TEA), etc. evidences that the electron-rich vinyloxy group does act as an important role in the SSQE of VOENI. C₆₀ can also quench the fluorescence of the polymers, and an upward deviation from the linearity of the Stern–Volmer plot was observed showing that C₆₀ acted as a powerful electron donor to quench the fluorescence of the copolymer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1111–1116, 1998     

Acyclic diene metathesis polymerization of tailor-made monomers towards sequence-regulated vinyl copolymers

 Acyclic diene metathesis polymerization (ADMET) enables convenient transfer of sequential information of the designed monomers to the corresponding sequence-regulated copolymers. In this study, two structurally symmetric monomers, M1 and M2, were synthesized via atom transfer radical addition (ATRA) of diethyl meso-2,5-dibromohexanedioate with 1,5-hexadiene and 1,7-octadiene, respectively. Thus, sequenced segment of VB-EA-EA-VB (VB and EA represent vinyl bromide and ethyl acrylate, respectively) was incorporated into the ADMET diene monomers. ADMET polymerization of these two monomers with Grubbs first generation catalyst (Grubbs-I) was performed in CH₂Cl₂ at 40℃ for 5 days under nitrogen purge. Effects of catalyst amount, monomer concentration and methanol precipitation on the M_p and PDI of polymers were investigated by GPC, and the structures of the formed polymers were characterized by NMR. Our results indicate that using 3.0 mol% of Grubbs-I to monomer can afford polymers with high M_p. Moreover, selective precipitation in methanol enables complete removal of low molecular weight components from the crude products. Meanwhile, M2 exhibits higher ADMET polymerization reactivity than M1 due to its capability of suppressing negative neighboring group effect.     

Polymerizations of vinyl methacrylate and vinyl acrylate

Both vinyl methacrylate (VMA) and vinyl acrylate (VA) were homopolymerized by n-butyllithium catalyst at ?78°C. Both of the anionic polymers were soluble in common organic solvents, and only vinyl group was contained in the polymers. Both of the monomers were homopolymerized by free-radical catalysts under different conditions. The soluble polymers were obtained under low monomer concentrations and at low conversions. It was estimated by NMR and infrared spectroscopy that both the soluble polymers contained mainly a vinyl group, similar to the anionic polymers. The soluble VMA polymers comprised 10–20% cyclic units for monomer concentrations ranging from 1.8 to 0.5 mole/I. The soluble VA polymers comprised 50–60% cyclic units for monomer concentrations ranging from 0.9 to 0.3 mole/l. It was suggested that the cyclic units did not consist of γ-lactone but of larger-membered rings than δ-lactone or of ladder structural units. The difference between the cyclization content of poly-VMA and that of poly-VA might be explained by the copolymerization data of the reference monomers.     

Semiconducting polymers based on charge-transfer complexes. I. Synthesis of electron-donor-containing poly-N-acylethylnimines

Polymers were made which contained 10-methyl, 3-phenothiazinyl, and 4-(methylthio)phenoxy electron-donating groups on side chains. N-Acyl-substituted poly-ethylenimines were chosen because the repeat distance along the polymer chain is the same as the repeat distance in most aromatic charge-transfer complexes (about 6.4 Å) and the side chains do not interfere with each other. This paper describes synthetic routes for preparation of these electron-donor-containing polymers. Synthesis of a polyacrylate donor is also described.     

Free‐radical crosslinking copolymerization of 2,2′‐azobis[N‐(2‐propenyl)‐2‐methylpropionamide] with vinyl benzoate resulting in polymeric azo initiators

2,2′‐Azobis[N‐(2‐propenyl)‐2‐methylpropionamide] (APMPA) with two carbon–carbon double bonds and an azo group was copolymerized with vinyl benzoate (VBz) at 60 °C, resulting in azo groups containing VBz/APMPA prepolymers and crosslinked polymers as soluble and insoluble polymeric azo initiators, respectively. The polymerization characteristics of APMPA as a novel diallyl monomer were clarified with the rate and degree of polymerization and the monomer reactivity ratios. The gelation behaviors in VBz/APMPA crosslinking copolymerizations were examined in detail with a comparison of the actual gel point and the theoretical gel point calculated according to Stockmayer's equation with the tentative assumption of equal reactivity for both vinyl groups belonging to VBz and APMPA. The effectiveness of the resulting branched or crosslinked poly(VBz‐co‐APMPA)s as soluble or insoluble polymeric azo initiators, respectively, at providing graft polymers through the cleavage of azo groups at an elevated temperature was examined by the polymerization of allyl benzoate at 120 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 317–325, 2002     

Solution polymerization of vinyl monomers in the presence of poly(N-acetyliminoethylene) macroazoinitiators

New block copolymers with poly(N-acetyliminoethylene) and vinyl sequences were obtained by a two-step synthetic approach. In the first stage macroinitiators of poly(N-acetyliminoethylene) type, with azo groups inserted in the main chain, were prepared. They were latter used in the radical polymerization of some vinyl monomers [styrene, methacrylic acid, methyl methacrylate, butyl methacrylate, β-(N-carbazolyl)ethyl acrylate, β-(methacryloyfoxy)ethyl 3,5-dinitrobenzoate]. The resulting block copolymers were characterized by spectral methods, elemental analysis, gel permeation chromatography, and electron microscopy. The kinetic study of the thermal and photochemical decomposition of the synthesized macroazoinitiators, as well as the polymerization data, suggest a dependence of their initiating efficiency on the length of the poly(N-acetyliminoethylene) segments. © 1994 John Wiley & Sons, Inc.     

Anionic polymerization. VI. Effect of polar modifiers on alkylsodium and alkylpotassium polymerization of butadiene

It was found that N,N,N′,N′-tetramethylethylene diamine and hexamethyl phosphorus triamide minimize chain transfer reactions in the polymerization of 1,3-butadiene in hydrocarbon solvent with alkylsodium or alkylpotassium initiators. The polymers obtained with alkylsodium initiators had a high molecular weight and high vinyl content at 90–95% conversion. The molecular weight of the polybutadiene made by alkylsodium and alkylpotassium initiators was dependent on the polymerization temperatures and modifier ratios, but the vinyl contents were independent of the modifier ratios. Vinyl contents of alkylpotassium-initiated polymers showed a slight dependency on polymerization temperature; the vinyl contents of alkylsodium-initiated polymers were independent of temperature. Addition of lithium tert-butoxide and potassium tert-amylate to these initiators in the presence of the modifiers affected the molecular weight but not the microstructure.     

Low-temperature polymerization of lactams by using as catalyst the salt derived from NaAlEt4 and monomer and with several compounds as initiator

Low-temperature polymerization of α-pyrrolidone, α-piperidone, and ?-caprolactam was examined by using the salts derived from NaAlEt₄ and monomer, sodium lactamates, or the salt derived from AlEt₃ and monomer as catalyst and with N-acetyl lactams, ethyl acetate, or lactones as initiator. Sodium lactamate catalyst gave unsatisfactory results in the cases of ethyl acetate or lactones initiators, and gave the following order for the relative efficiency of initiators: N-acetyl lactam > ?-caprolactone ≥ ethyl acetate > β-propiolactone. The polymerization results obtained by the salt from NaAlEt₄ catalyst–ethyl acetate initiator system were nearly the same as those with N-acetyl lactam. The increases in the degree of polymerization and in the yield of polymer were observed in case of the salt from NaAlEt₄ catalyst-lactone initiator system, particularly in the cases of α-piperidone and ?-caprolactam. Also an incorporation of initiator into polymer chain was observed.     

Polycationic salts. VI. Synthesis and in vitro studies of 2-ionene oligomer derivatives of styrene as bile acid sequestering agents

Several vinylbenzyltri-n-alkylammonium salts were prepared via the Menshutkin reaction in high yields by the reaction of vinyl benzyl chloride (VBC) and tertiary amines. Additional salts based on 2-ionene oligomers were synthesized via a sequential Menshutkin reaction. The 2-ionene oligomers were further reacted with VBC to afford the vinyl benzyl chloride-2-ionene halide monomers in nearly quantitative yield. The monomers were polymerized in either aqueous or organic solvents with azo initiators in high yield with correspondingly high inherent viscosities. The polymers were measured spectrophotometrically for their bile acid sequestering activity with an in vitro enzymatic reaction. Several of the measured polymers exhibited 15–28% greater activity relative to cholestyramine. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 701–713, 2004     

Vinyl monomers bearing chromophore moieties and their polymers. III. Synthesis and photochemical behavior of acrylic monomers having phenothiazine moieties and their polymers

Four acrylic monomers bearing phenothiazine moieties, i.e., N-acrylyl-phenothiazine (APT), N-acrylyl-2-chlorophenothiazine (ACPT), N-acrylyl-2-acetylphenothiazine (AAPT), and 10-acrylyl-1-azaphenothiazine (AAzPT) were synthesized by dehydrohalogenation of the corresponding N-(β-chloropropionyl)-substituted phenothiazine derivatives with 1,8-diazabicyclo[5.4.0]undec-5-ene (DBU). These monomers could easily be polymerized by initiation with AIBN. The emission fluorescence spectra of the monomers and their polymers were recorded, which showed that the polymers displayed much stronger fluorescence than their corresponding monomers at the same chromophore concentrations. This phenomenon, as termed as “structural self-quenching effect,” was commonly observed for acrylic monomers bearing chromophore moieties and ascribed to the coexistence of the electron-donating chromophore and the electron-accepting double bond in the same molecule. Because of the formation of exciplex, the monomer APT, as well as ACPT, AAPT, AAzPT, and their polymers, could initiate the photopolymerization of AN. The charge transfer phenomenon between P(APT), P(ACPT), and C₆₀ was also explored. © 1996 John Wiley & Sons, Inc.     

Phosphonobetaine/sulfur dioxide copolymer by Butler’s cyclopolymerization process

The zwitterionic monomer, ethyl 3-(N,N-diallylammonio)propanephosphonate and sulfur dioxide were cyclocopolymerized in DMSO using azobisisobutyronitrile or ammonium persulfate as initiators to afford a pH-responsive polyphosphonobetaine/SO₂ (PPB/SO₂) copolymer. The polymers, on treatment with HCl and NaOH, gave the aqueous solutions of the corresponding cationic polyphosphononic acid (CPP) and anionic polyphosphonate (APP). The solution properties of the PPB having two pH-responsive functionalities were investigated in detail by potentiometric and viscometric techniques. Basicity constants of the amine and phosphonate groups in APP were found to be “apparent” and as such follow the modified Henderson–Hasselbalch equation. The incorporation of SO₂ moiety has resulted in the decrease of basicity constant of the nitrogens in the copolymer by staggering ?2 units of log K in compare to that of the corresponding homopolymer. The basicity difference is expected to have an effect on the chelating properties of the polymers. In contrast to many polycarbo- and -sulfobetaines, the PPB was all found to be soluble in salt-free water as well as in salt (including Ca²⁺ and Li⁺)-added solutions. The PPB demonstrated ‘antipolyelectrolyte’ viscosity behavior and found to have higher viscosity values in LiCl than in NaCl or NaI.     

Preparation and polymerization of N-(1,1-dimethyl-3-hydroxybutyl) acrylamide and N-(1,1-dimethyl-3-hydroxybutyl)methacrylamide

The syntheses of N-(1,1-dimethyl-3-hydroxybutyl)acrylamide and the corresponding methacrylamide by reduction of the oxobutyl acrylamides are described. These monomers are colorless liquids which are soluble in water and many organic solvents. They polymerize readily to form homopolymers and copolymers with other vinyl monomers. The preparation of polymers containing these repeating units by reduction of polymers of diacetone acrylamide and diacetone methacrylamide is also described.     

Vinyl-gem-dichlorocyclopanes in radical polymerization

Vinyl-gem-dichlorocyclopropanes in the presence of radical type initiators undergo isomerizational homo-and copolymerization with vinyl monomers to form copolymers with the random distribution of monomer units in the macrochain. As compared to vinyl monomers like methyl methacrylate, acrylonitrile, and styrene they are considerably less active. By means of ¹³C NMR spectroscopy it was shown that vinyl-gem-dichlorocyclopropanes polymerized forming steroblock polymers of mainly trans-structure.     

Cationic polymerization of α,β-disubstituted olefins. V. Reactivity of propenyl alkyl ethers in cationic polymerization

To elucidate the effect of the introduction of a methyl group in the β-position of a vinyl monomer, propenyl alkyl ethers were copolymerized with vinyl ethers having the same alkoxy group. Propenyl alkyl ethers with an unbranched alkoxy group (ethyl or n-butyl propenyl ether) were more reactive than the corresponding vinyl ethers. This behavior is quite different from that of β-methylstyrene derivatives. However, propenyl alkyl ethers with branched alkoxy groups at the α carbon atom (isopropyl or tert-butyl propenyl ether) were less reactive than the corresponding vinyl ethers. Also, cis- isomers were more reactive than the trans isomers, regardless of the kind of alkoxy group and the polarity of the solvent.     

Sodium hydride-initiated polymerizations of vinyl monomers in aprotic solvents

Polymerizations of several vinyl monomers at 25°C in aprotic solvents (dimethyl sulfoxide, N,N-dimethylacetamide, and hexamethylphosphoric triamide) using sodium hydride dispersion as initiator yield low to intermediate molecular weight polymers. The molecular weight of the resulting polymer as well as the mode of initiation depends on the monomer and aprotic solvent used. Initiation of polymerization of monomers with available α hydrogens (methyl acrylate, acrylonitrile) involves monomer anion, while initiation of a monomer with no α hydrogen (methyl methacrylate) proceeds by a more complex mechanism. In contrast, initiation of styrene and α-methylstyrene proceeds by dimsyl anion addition to monomer in dimethylsulfoxide. Although the triad tacticities and number-average molecular weights of poly(methyl methacrylate) samples obtained from all three aprotic solvents are nearly the same, poly(methyl methacrylates) prepared in dimethyl sulfoxide and N,N-dimethylacetamide give polymers having polydispersities of ～3, while a very polydisperse polymer is obtained in hexamethylphosphoric triamide.     

Polymerizations of some diene monomers. Preparations and polymerizations of vinyl methacrylate,allyl methacrylate,N-allylacrylamide,and N-allylmethacrylamide

Vinyl methacrylate, allyl methacrylate, N-allylacrylamide, and N-allylmethacrylamide were prepared, and these monomers were polymerized in toluene by α,α-azobisisobutyronitrile catalyst. Cyclization content of poly(vinyl methacrylate) was estimated by infrared spectroscopy to be 50–60% at low conversions, but at the high conversions, due to gelation the polymers were insoluble in the usual organic solvents. Allyl methacrylate did not produce any soluble polymer, even at a low conversion, in contrast with poly-(vinyl methacrylate). Poly-N-allylacrylamide and poly-N-allylmethacrylamide were also insoluble in common solvents. It was assumed that the polymers from monomers containing the allyl group might form crosslinks as a result of allyl resonance stabilization.