Structural Self-quenching Effect Research Articles

Atom transfer radical polymerization of a novel quinoline derivative monomer and fluorescent property

A novel functional monomer incorporating quinoline derivative moiety as the side group, 2-[4-(2,7,7-trimethyl-3-ethoxycarbonyl-5-oxo-1,4,5,6,7,8-hexhydricquinoline)phenoxyl] ethylmethacrylate (HQPEMA), was synthesized and polymerized utilizing atom transfer radical polymerization (ATRP) technique. 2-(4-Chloromethylphenyl)benzoxazole (CMPB) and CuCl/PMDETA were used as the initiator and catalyst, respectively. GPC, 1H NMR and fluorescent emission spectroscopy were conducted for characterization of polymers. The linear increase of number average molecular weight ( M n) versus conversion and the relatively narrow molecular weight distribution ( M w/ M n) of the obtained polymers confirmed that ATRP of HQPEMA was carried out successfully. In addition, the fluorescence “structural self-quenching effect” was observed in the DMF solution of the monomer HQPEMA, which bearing both electron-donating chromophore group and electron-accepting C C bond. We also found that the fluorescence properties of the newly obtained polymers containing quinoline chromophore depended on both the monomer concentration in solution and the polarity of solvents. The emission of the polymer film showed that the emission peak maxima of the polymer film shifted 50 nm towards high wavelength with respect to the polymer in DMF solution due to the intermolecular or intramolecular interactions of the polymer chains.

Bismaleimides Having Electron-Donating Chromophore Moieties: A New Approach Toward Monitoring the Process of Curing Based on Their Fluorescence Behavior

Bismaleimides having electron-donating diphenylmethylamine or triphenylamine moieties (A(=)-D(*)-A(=)), as well as their saturated model compounds were synthesized. Their fluorescence behavior was found to show a strong fluorescence structural self-quenching effect (SSQE). On the basis of this strong SSQE of A(=)-D(*)-A(=) bismaleimides, a new fluorescence approach can be developed to monitor the curing process in bismaleimide resins, which is in agreement with the results from FT-IR and 1H NMR analyses.

Vinyl monomers bearing chromophore moieties and their polymers. IX. Initiation and photochemical behavior of water and liposoluble acrylic monomers having pyrimidinyl moiety and their polymers

Two acrylic monomers bearing a pyrimidinyl moiety, N-acryloyl-N′-2-pyrimidinylpiperazine (APMP) and N-methacryloyl-N′-2-pyrimidinylpiperazine (MPMP), are prepared by reactions of N-2-pyrimidinylpiperazine with corresponding acryloyl chlorides in the presence of triethylamine. APMP and MPMP can be polymerized either by using radical initiators such as azobisisobutylonitrile or potassium persulfate (KPS) or by UV light irradiation without any sensitizer. APMP, MPMP, and their polymers are water soluble and liposoluble. They can act as sensitizers to initiate the photopolymerizations of acrylonitrile (AN) in DMF and acrylamide (AAm) or N-acryloylmorpholine (AMPL) in an aqueous medium. They can also act as one component of a redox initiation system by combining with KPS to initiate the polymerization of AAm in an aqueous medium, and a superhigh molecular weight up to 106–107 for P(AAm) or 105–106 for P(AMPL) is obtained. The above polymerizations are pursued kinetically. The mechanism of the photopolymerizations initiated by MPMP or P(MPMP) are confirmed by an electron spin resonance study. By the fluorescent analysis of PAN and P(AAm) initiated by MPMP, APMP, or their polymers we confirm that they not only initiate the polymerization but also enter the polymer chains. The fluorescence spectra of MPMP, APMP, and their polymers are recorded. A fluorescence structural self-quenching effect is also observed. The fluorescence of P(MPMP) can be quenched by adding electron-deficient unsaturated compounds such as methacrylonitrile, AN, fumaronitrile, tetracyanoethylene, methyl acrylate, and methyl methacrylate and the correlation between the Stern–Volmer constants and the electron deficiency of the quenchers is described. The fluorescence quenching of P(MPMP) by a water-soluble C60 derivative is also demonstrated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 19–28, 2000

Vinyl monomers bearing chromophore moieties and their polymers. XI. Synthesis and photochemical behavior of carbazole-containing methacrylic monomers and their polymers

Three carbazole-containing methacrylic monomers, 2-(N-carbazolyl)ethyl methacrylate(CzEMA), 6-(N-carbazolyl)hexyl methacrylate(CzHMA), and 11-(N-carbazolyl)undecyl methacrylate (CzUMA), and their saturated model compounds, 2-(N-carbazolyl)ethyl isobutyrate, 6-(N-carbazolyl)hexyl isobutyrate, and 11-(N-carbazolyl)undecyl isobutyrate, were synthesized and polymerized. UV absorption spectra showed that there was either negligible or no interaction between the carbon–carbon double bond of the methacrylic group and the carbazolyl chromophore moiety in the ground state for these monomers. Fluorescence spectra of the monomers, their model compounds, and the polymers were recorded in the solvents with different polarities. CzEMA exhibited the fluorescence structural self-quenching effect (SSQE), but CzHMA and CzUMA did not. In addition, the SSQE of CzEMA depended strongly on the polarity of the solvents. That is, the stronger the polarity of a solvent was, the more obvious the SSQE was. Therefore, the SSQE of CzEMA mainly was caused by the intramolecular charge-transfer interaction between the excited electron-donating carbazolyl chromophore moiety and the electron-accepting carbon–carbon double bond of the methacrylic group. This was confirmed by the fluorescence-decay curves and the fluorescence lifetimes of the monomers, their model compounds, and the polymers. The monomers, their model compounds, and the polymers initiated the photopolymerization of methyl methacrylate (MMA) upon UV irradiation. CzEMA showed greater initiation ability than the other two monomers and their model compounds; this was ascribed to the photoinduced intramolecular charge-transfer interaction. The higher initiation efficiency of the homopolymers compared to that of the copolymers with MMA was interpreted as the result of singlet energy migration of the excited carbazolyl chromophores along the polymer chains. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 679–688, 2000

Vinyl monomers bearing chromophore moieties and their polymers. XI. Synthesis and photochemical behavior of carbazole‐containing methacrylic monomers and their polymers

Three carbazole-containing methacrylic monomers, 2-(N-carbazolyl)ethyl methacrylate(CzEMA), 6-(N-carbazolyl)hexyl methacrylate(CzHMA), and 11-(N-carbazolyl)undecyl methacrylate (CzUMA), and their saturated model compounds, 2-(N-carbazolyl)ethyl isobutyrate, 6-(N-carbazolyl)hexyl isobutyrate, and 11-(N-carbazolyl)undecyl isobutyrate, were synthesized and polymerized. UV absorption spectra showed that there was either negligible or no interaction between the carbon–carbon double bond of the methacrylic group and the carbazolyl chromophore moiety in the ground state for these monomers. Fluorescence spectra of the monomers, their model compounds, and the polymers were recorded in the solvents with different polarities. CzEMA exhibited the fluorescence structural self-quenching effect (SSQE), but CzHMA and CzUMA did not. In addition, the SSQE of CzEMA depended strongly on the polarity of the solvents. That is, the stronger the polarity of a solvent was, the more obvious the SSQE was. Therefore, the SSQE of CzEMA mainly was caused by the intramolecular charge-transfer interaction between the excited electron-donating carbazolyl chromophore moiety and the electron-accepting carbon–carbon double bond of the methacrylic group. This was confirmed by the fluorescence-decay curves and the fluorescence lifetimes of the monomers, their model compounds, and the polymers. The monomers, their model compounds, and the polymers initiated the photopolymerization of methyl methacrylate (MMA) upon UV irradiation. CzEMA showed greater initiation ability than the other two monomers and their model compounds; this was ascribed to the photoinduced intramolecular charge-transfer interaction. The higher initiation efficiency of the homopolymers compared to that of the copolymers with MMA was interpreted as the result of singlet energy migration of the excited carbazolyl chromophores along the polymer chains. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 679–688, 2000

Synthesis and fluorescence behavior of 3-methacryamide-9-carbazole and its polymer

A novel acrylic monomer-bearing carbazole chromophore, 3-methacrylamide-9-ethyl-carbazole and its model compound 3-isobutyramide-9-ethylcarbazole were synthesized by reaction of 3-amino-9-ethyl carbazole and the corresponding acyl chloride in the presence of triethylamine. It can be polymerized easily by using azo-bisisobutyronitrile as an initiator or photopolymerized without any sensitizer. The photochemical behavior of 3-methacrylamide-9-ethyl-carbazole, its polymer and 3-isobutyramide-9-ethylcarbazole were investigated by recording the fluorescence spectra in N,N-dimethylformamide. It was found that the fluorescence intensity of the monomer is dramatically lower than those of its polymer and the model compound in the same chromophore concentration. This phenomenon, termed as the ‘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 within one molecule. The strong fluorescence of the polymer can be quenched by adding electron-deficient monomers having no chromophore moieties such as methyl methacrylate and acrylonitrile, and the Stern–Volmer constants were determined. It is observed that the higher the electron deficiencies of the quenchers, the higher the Stern–Volmer constants, implying a stronger quenching effect.Copyright © 2000 John Wiley & Sons, Ltd.

Vinyl monomers bearing chromophore moieties and their polymers. XII. Synthesis and fluorescence behavior of vinyloxy monomers having 1,8-naphthalimide moiety with different spacer lengths and their polymers

Two vinyloxy monomers bearing electron-accepting naphthalimide with different spacer lengths, i.e.N-(2-vinyloxyethyl)-1,8-naphthalimide (VOENI) and N-(6-vinyloxyhexyl)-1,8-napholimide (VOHNI) were synthesized by the reaction of potassium 1,8-naphthalimide with corresponding ω-chloroalkyl vinyl ethers. These monomers can be polymerized cationically, and copolymerized radically with N-actoxyethylmaleimide (AEMI). The fluorescence behaviors of the two monomers were studied by comparing with that of their saturated model compound in order to further understand the nature of fluorescence structural self-quenching effect (SSQE). It was found that the SSQE of these monomers depends on the spacer lengths between the naphthalimide moiety and the vinyloxy group, as well as the properties of solvents used. It is demonstrated that the SSQE of these monomers occurs mainly via the intramolecular charge transfer interaction between the electron-donating vinyloxy group and the electron-accepting 1,8-naphthalimide chromophore upon UV irradiation. In addition, the fluorescence behavior of the copolymer of VOENI and AEMI was also studied. Copyright © 2000 John Wiley & Sons, Ltd.

Manufacture of modified poly(vinyl acetal) showing fluorescence and molecular recognition

Poly(vinyl acetal) from poly(vinyl alcohol) and 4-dimethylaminobenzaldehyde (DMAB) is synthesized. Fluorescence behavior of the polymer is investigated in acetic acid glacial (HAc), dimethylsulfoxide (DMSO), and dimethylformamide (DMF) solvents. Fluorescence emission intensities of the polymer solutions are different with the change of concentration. The result suggests that the maximum fluorescence emission intensities of the polymer solutions depend on the optimal concentration of the polymer. It has been found that the fluorescence intensity of DMAB is dramatically lower than that of the polymer in the same chromophore concentration, and such phenomenon is termed as structural self-quenching effect (SSQE). The strong fluorescence of the polymer can be quenched by adding electron-deficient monomers which have no chromophore moieties such as lactic acid, adenine, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The result indicates that the polymer can recognize these biologic small molecules. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2385–2390, 1999

Vinyl monomers bearing chromophore moieties and their polymers. VIII. synthesis and fluorescence behavior of a vinyloxy monomer having an electron-accepting chromophore moiety,p-((vinyloxy)methyl)benzonitrile, and its polymers

A vinyloxy monomer having an electron-accepting chromophore moiety, p-((vinyloxy)methyl)benzonitrile (VOMBN), was synthesized by reaction of p-(hydroxymethyl)benzonitrile with ethyl vinyl ether (EVE) in the presence of mercuric acetate. VOMBN can easily be cationically homopolymerized and copolymerized with EVE by using Lewis acids such as boron trifluoride etherate (BF3 · OEt2) as a catalyst and radically copolymerized with maleic anhydride (MAn) using AIBN as an initiator. The fluorescence behaviors of VOMBN, its copolymer P(VOMBN-co-MAn), and its saturated model compound p-(ethoxymethyl)benzonitrile (EOMBN) were investigated in acetonitrile. It has been found that the fluorescence intensity of VOMBN is much lower than its copolymer and EOMBN at the same chromophore concentration. A fluorescence “structural self-quenching effect” (SSQE) is also observed for VOMBN as we have reported previously [Li, F. M.; Chen, S. J.; Li, Z. C.; Qiu, J. J Polym Sci Polym Chem 1996, 34, 1881]. This phenomenon has been attributed to the inter- and intramolecular charge transfer interaction between the electron-accepting cyanophenyl chromophore and the electron-donating vinyloxy group in the same molecule. The dependence of the fluorescence intensity of VOMBN on solvents of different viscosities is evidence that the SSQE of VOMBN mainly occurs intramolecularly. The fluorescence of EOMBN and P(VOMBN-co-MAn) was quenched by a series of electron-rich vinyloxy compounds which do not have chromophore moieties, such as dihydrofuran (2H-furan), dihydropyran (2H-pyran), furan, and EVE. It is observed that the higher the electron-donating ability of the quenchers, the greater the quenching efficiency. P(VOMBN) and the random copolymers of VOMBN with EVE show broader fluorescence spectra as compared to the alternating copolymer P(VOMBN-co-MAn). This indicates that there is a mutual interaction between the adjacent cyanophenyl groups in P(VOMBN) and P(VOMBN-co-EVE), whereas such an interaction does not exist for P(VOMBN-co-MAn) in which the cyanophenyl groups are isolated by the rigid succinic anhydride rings. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 179–187, 1999

Vinyl monomers bearing chromophore moieties and their polymers. VII. Synthesis, photochemical, and initiation behavior of acrylic monomers bearing phenothiazine oxide moieties and their polymers

Four acrylic monomers bearing phenothiazine oxide moieties, that is, N-acryloyl-phenothiazine-5-oxide (APTO), N-acryloyl-2-chlorophenothiazine-5-oxide (ACPTO), N-acryloyl-phenothiazine-5,5-dioxide (APTDO), and N-acryloyl-2-chlorophenothiazine-5,5-dioxide (ACPTDO) were synthesized by oxidation of corresponding N-acryloyl-phenothiazine (APT) and N-acryloyl-2-chlorophenothiazine (ACPT) using sodium perborate as an oxidant. These monomers could easily be polymerized by initiation of AIBN. The emission fluorescence spectra of the monomers and their polymers were recorded, and the results indicated that these 4 new monomers possess a fluorescence structural self-quenching effect (SSQE), as we have reported previously. Moreover, with the change of the electronic structure of sulfur atom in the phenothiazine chromophore, that is, from sulfide to sulfoxide and sulfone groups, the tendency of SSQE of these monomers is in the order of APT > APTO > APTDO. This would be ascribed mainly to the decrease of electron-donating abilities of monomers in a sequence of sulfide, sulfoxide, and sulfone groups; that is, at the sulfur atom of these monomers, APT has 2 lone-pair electrons, APTO has 1 lone-pair electrons, and APTDO completely loses its lone-pair electrons. Based on the exciplex formation, the monomers APTO, APTDO, ACPO, and ACPTDO could act as sensitizers for the photopolymerization of acrylonitrile (AN). The combination of APTO or ACPTO with organic peroxides such as BPO could also initiate the polymerization of vinyl monomers, such as AN, by redox nature. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1191–1199, 1998

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

Vinyl monomers bearing chromophore moieties and their polymers. VI. Synthesis and photochemical behavior of acrylic monomer bearing phenoxazine moiety and its polymer

An acrylic monomer having phenoxazine moiety, i.e., N-acryloylphenoxazine (APO), has been synthesized by dehydrochlorination of N-(3-chloropropionyl)phenoxazine with 1,5-diazabicyclo[5.4.0]undec-5-ene in dimethyl sulfoxide. The monomer can be polymerized with AIBN as an initiator. The photochemical behavior, including the fluorescence and photosensitizing properties of this monomer and its polymer, has been studied. It has been recorded that the absorption spectrum of polymer P(APO) displays a few blue shifts compared with its monomer APO. It has also been observed that the fluorescence emission intensity of the monomer is dramatically lower than that of its polymer at the same chromophore concentration. This may be ascribed to the charge transfer interacting between the coexisting electron-accepting acrylic carbon-carbon double bond and the electron-donation phenoxazine moiety in APO, intramolecularly or intermolecularly on excitation. The fluorescence of the APO polymer, which does not have carbon-carbon double bond, can be quenched by electron-deficient unsaturated nitriles and esters, clarifying that the electron-deficient carbon-carbon double bond does play an important role for the fluorescence quenching of the monomer. Thus, we term such phenomena as structural self-quenching effect, differing from the concentrational self-quenching effect, which is caused mainly by concentrational factors. The fluorescence quenching of P(APO) by C60 has also been demonstrated. The formation of the charge transfer complex of P(APO) with C60 in the ground state is revealed by the upward deviation from the linearity of the Stern-Volmer plot. APO can act as a photoinitiator to sensitize the photopolymerization of vinyl monomers such as acrylonitrile in dimethyl formamide and pursued kinetically. From the ultraviolet analysis of the PAN sensitized by APO, it is proved that APO not only sensitizes the photopolymerization of AN, but also incorporates in the PAN chain. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:481–489, 1997

Vinyl monomers bearing chromophore moieties and their polymers. VI. Synthesis and photochemical behavior of acrylic monomer bearing phenoxazine moiety and its polymer

An acrylic monomer having phenoxazine moiety, i.e., N-acryloylphenoxazine (APO), has been synthesized by dehydrochlorination of N-(3-chloropropionyl)phenoxazine with 1,5-diazabicyclo[5.4.0]undec-5-ene in dimethyl sulfoxide. The monomer can be polymerized with AIBN as an initiator. The photochemical behavior, including the fluorescence and photosensitizing properties of this monomer and its polymer, has been studied. It has been recorded that the absorption spectrum of polymer P(APO) displays a few blue shifts compared with its monomer APO. It has also been observed that the fluorescence emission intensity of the monomer is dramatically lower than that of its polymer at the same chromophore concentration. This may be ascribed to the charge transfer interacting between the coexisting electron-accepting acrylic carbon-carbon double bond and the electron-donation phenoxazine moiety in APO, intramolecularly or intermolecularly on excitation. The fluorescence of the APO polymer, which does not have carbon-carbon double bond, can be quenched by electron-deficient unsaturated nitriles and esters, clarifying that the electron-deficient carbon-carbon double bond does play an important role for the fluorescence quenching of the monomer. Thus, we term such phenomena as structural self-quenching effect, differing from the concentrational self-quenching effect, which is caused mainly by concentrational factors. The fluorescence quenching of P(APO) by C60 has also been demonstrated. The formation of the charge transfer complex of P(APO) with C60 in the ground state is revealed by the upward deviation from the linearity of the Stern-Volmer plot. APO can act as a photoinitiator to sensitize the photopolymerization of vinyl monomers such as acrylonitrile in dimethyl formamide and pursued kinetically. From the ultraviolet analysis of the PAN sensitized by APO, it is proved that APO not only sensitizes the photopolymerization of AN, but also incorporates in the PAN chain. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:481–489, 1997

Vinyl monomers bearing chromophore moieties and their polymers. IV. Fluorescence and photosensitizing behavior of 8-acryloyloxyquinoline and its polymer

Acrylic monomers bearing electron-donating quinolyl moiety, i.e., 8-acryloyloxyquinoline (AQ) was prepared and polymerized. It was found that the fluorescence intensity of AQ was much lower than that of P(AQ) at the same chromophore concentration. The fluorescence of P(AQ) could be quenched by electron-deficient vinyl monomers, such as acrylonitrile (AN) and methyl methacrylate (MMA). 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. The photopolymerization of acrylonitrile (AN) sensitized by AQ and P(AQ) as well as combining with carbon tetrabromide (CBr4) was studied kinetically. From the rates of the polymerization (Rp) and overall activation energies obtained for these four systems, it was found that Rp sensitized by the binary systems was much higher than by AQ or P(AQ) alone, while the molecular weights of the resulting P(AN) were lower. The fluorescent analysis of the resulting P(AN) in solution showed that the sensitizers also entered into the P(AN) chains. A mechanism of charge transfer complex (CTC) formation was tentatively suggested for the photopolymerization of AN initiated by these four systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1087–1093, 1997

Vinyl monomers bearing chromophore moieties and their polymers. IV. Fluorescence and photosensitizing behavior of 8‐acryloyloxyquinoline and its polymer

Acrylic monomers bearing electron-donating quinolyl moiety, i.e., 8-acryloyloxyquinoline (AQ) was prepared and polymerized. It was found that the fluorescence intensity of AQ was much lower than that of P(AQ) at the same chromophore concentration. The fluorescence of P(AQ) could be quenched by electron-deficient vinyl monomers, such as acrylonitrile (AN) and methyl methacrylate (MMA). 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. The photopolymerization of acrylonitrile (AN) sensitized by AQ and P(AQ) as well as combining with carbon tetrabromide (CBr4) was studied kinetically. From the rates of the polymerization (Rp) and overall activation energies obtained for these four systems, it was found that Rp sensitized by the binary systems was much higher than by AQ or P(AQ) alone, while the molecular weights of the resulting P(AN) were lower. The fluorescent analysis of the resulting P(AN) in solution showed that the sensitizers also entered into the P(AN) chains. A mechanism of charge transfer complex (CTC) formation was tentatively suggested for the photopolymerization of AN initiated by these four systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1087–1093, 1997

Synthesis and photochemical behavior of 2-(N-acridonyl)ethyl methacrylate and its polymer

A polymerizable photosensitizer, 2-(N-acridonyl)ethyl methacrylate (AEMA), containing both aromatic ketone and aromatic tertiary amine moieties in the same molecule, was prepared by reaction of N-hydroxyethyl acridone (HEA) and methacryloyl chloride in the presence of triethylamine (TEA). HEA was obtained by reaction of acridone with ethylene carbonate. The photochemical behavior including photoinitiation and fluorescence properties of AEMA and its polymer P(AEMA) were studied. It was found that the photoinitiation efficiency of monomeric AEMA is lower than that of its polymer for the photopolymerization of acrylonitrile (AN) in DMF. By the kinetic study and the analysis of recorded electron spin resonance spectra of the photoinitiation systems of AEMA or AEMA-dimethylaminoethyl methacrylate (DMAEMA) trapped by 2-methyl-2-nitritopropane (MNP), the mechanism is deduced to be similar to that of the benzophenone-TEA system. The recorded fluorescence spectra show that AEMA and P(AEMA) possess a strong fluorescence emission peak at 410 and 439 nm, respectively. The concentration self-quenching effect was observed with maximum intensities at a concentration of 8.6 X 10 -5 mol/L in DMF for both AEMA and P(AEMA). Even though AEMA has a tertiary amino group and an electron-deficient acrylic double bond in the same molecule, it did not display structural self-quenching effect as we reported previously. This may be due to the two benzene rings in acridone that lessen the electron-donating ability of the N atom. The fluorescence quenching of AEMA and P(AEMA) by electron-donating and electron-accepting compounds was also investigated.

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.

Vinyl monomers bearing chromophore moieties and their polymers. I. Initiation and photochemical behavior of N‐acryloyl‐N′‐phenylpiperazines and their polymers

Two novel acrylic monomers bearing aromatic tertiary amino groups, i.e., N-acryloyl-N′-phenylpiperazine (APP) and N-methacryloyl-N′-phenylpiperazine (MPP) are synthesized by the reaction of N-phenylpiperazine and the corresponding acryloyl chlorides in the presence of triethylamine. They can be polymerized easily by using AIBN as an initiator or photopolymerized without any sensitizer. The photochemical behavior of APP, MPP, and their polymers are explored by recording the fluorescence spectra in solution. It has been found that the fluorescence intensities of these monomers are dramatically lower than those of their polymers in the same chromophore concentration, and such phenomenon is termed as “structural self-quenching effect” (SSQE). The strong fluorescence of these polymers can be quenched by adding electron-deficient monomers which have no chromophore moieties such as MMA, AN, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron-deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The SSQE displayed by APP and MPP make them useful as probes to pursue their photopolymerization process. As polymerizable aromatic tertiary amines, APP and MPP themselves or combining with organic peroxides such as BPO can initiate the photopolymerization or thermal polymerization of vinyl monomers such as MMA, AN by free radical nature, and at the same time enter the polymer chain. © 1996 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 34:1881–1888, 1996

Vinyl monomers bearing chromophore moieties and their polymers. I. Initiation and photochemical behavior ofN-acryloyl-N?-phenylpiperazines and their polymers

Two novel acrylic monomers bearing aromatic tertiary amino groups, i.e., N-acryloyl-N′-phenylpiperazine (APP) and N-methacryloyl-N′-phenylpiperazine (MPP) are synthesized by the reaction of N-phenylpiperazine and the corresponding acryloyl chlorides in the presence of triethylamine. They can be polymerized easily by using AIBN as an initiator or photopolymerized without any sensitizer. The photochemical behavior of APP, MPP, and their polymers are explored by recording the fluorescence spectra in solution. It has been found that the fluorescence intensities of these monomers are dramatically lower than those of their polymers in the same chromophore concentration, and such phenomenon is termed as “structural self-quenching effect” (SSQE). The strong fluorescence of these polymers can be quenched by adding electron-deficient monomers which have no chromophore moieties such as MMA, AN, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron-deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The SSQE displayed by APP and MPP make them useful as probes to pursue their photopolymerization process. As polymerizable aromatic tertiary amines, APP and MPP themselves or combining with organic peroxides such as BPO can initiate the photopolymerization or thermal polymerization of vinyl monomers such as MMA, AN by free radical nature, and at the same time enter the polymer chain. © 1996 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 34:1881–1888, 1996

Vinyl monomers bearing chromophore moieties and their polymers. II. Fluorescence and initiation behavior ofN-(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.