Novel excimer fluorescence method for monitoring polymerization: 1. Polymerization of methyl methacrylate

An excimer is formed by the association of an excited molecule with another molecule in its ground state. Such an excimer is characterized by a broad structureless fluorescence which is shifted to longer wavelengths compared to the fluorescence spectrum of the isolated molecule. Intramolecular excimer fluorescence has been observed in solutions of pyrene-labelled alkanes such as 1,3-bis-(1-pyrene)propane and 1,10-bis-(1-pyrene)decane.We have measured the solvent-viscosity dependence of the intensity ratio $\text{F}{}_{\mathrm{<mtext>M</mtext>}}\text{F}{}_{\mathrm{<mtext>D</mtext>}}$ for solutions of these pyrene-labelled alkanes in mixed solvents made of ethyl acetate and glycerol tripropionate. Here F_M and F_D are, respectively, the fluorescence intensity of the unassociated pyrene groups and that of the intramolecularly formed pyrene excimers. We have found that for each of the two pyrene-labelled alkanes, the ratio $\text{F}{}_{\mathrm{<mtext>M</mtext>}}\text{F}{}_{\mathrm{<mtext>D</mtext>}}$ increases with the increase in solvent viscosity. Further, we have shown that by adding a trace amount of 1,3-bis-(1-pyrene)propane or 1,10-bis-(1-pyrene)decanee to a polymerizing system, we can measure the ratio $\text{F}{}_{\mathrm{<mtext>M</mtext>}}\text{F}{}_{\mathrm{<mtext>D</mtext>}}$ to monitor in situ the polymerization reaction. polymerization;     

Excimer fluorescence technique for study of polymer-segment mobility: applications to pyrene-labelled poly(methyl methacrylate) and poly(methyl acrylate) in solution

An excimer fluorescence technique for the study of polymer-segment mobility has been developed and applied to pyrene-labelled poly(methyl methacrylate) and poly(methyl acrylate) polymers in solution. The results of the study have been interpreted in terms of Kramers' theory for the crossing of a potential barrier by a particle embedded in a viscous medium. The results show that the internal viscosity has a solvent-independent part and lead to an estimate of the dimensionless internal viscosity parameter introduced by Cerf.     

Characterization of blends of naphthalene-containing polymers with poly(alkyl methacrylates) by combined steady-state fluorescence spectroscopy and fluorescence decay measurements

The extent of mixing in two-component solution-cast films of poly(2-vinyl naphthalene) (P2VN) and poly(2-iso-propenyl naphthalene) (P2IPN) with poly(methyl methacrylate) and poly(n-butyl methacrylate) was studied by steady-state and time-resolved fluorescence spectroscopy. The steady-state fluorescence spectrum of 1% P2IPN in the two poly(alkyl methacrylates) evolves from 100% monomer emission (λ_max = 340 nm) to >70% excimer emission (λ_max = 390 nm) as its molecular weight increases from 1900 to 278000. Despite such clear-cut changes in the steady-state spectra on phase separation, the fluorescence decays were nonexponential for all mixed films. Triple-exponential decay functions were necessary to describe excimer decays at 430 nm and monomer decays at 340 nm. Moreover, the fluorescence decays varied slightly across the excimer emission band, and changed significantly when the polymer films were annealed. Studies on blends containing from 1 to 100% of P2VN and P2IPN established that this multicomppnent fluorescence decay behavior is intrinsicto the naphthalene-containing polymer phase, it is proposed that excimers formed between chromophores in meso and racemic dyads have different mean decay times and that imperfectly aligned chromophore pairs lead to an additional short-lived excimer decay component.     

Decay Lifetimes of Para-Substituted Polystyrene in Solid Films and in Dichloromethane

The fluorescence decay times of polystyrene, poly(4-bromostyrene), poly(4-chlorostyrene), poly(4-methylstyrene), poly(α-methylstyrene), poly(4-methoxystyrene), and poly(4-tert butylstyrene) were measured in solid films and in dichloromethane solution. A detailed analysis of the emission profile performed by nanosecond time resolved fluorescence spectroscopy confirmed the presence of monomer fluorescence as well as excimer fluorescence in both media. Monomer fluorescence decay times gave shorter times compared with that of excimer decay times in dichloromethane solution. Fluorescence from substituted polystyrene was mainly excimer fluorescence with shift of maximum emission to longer wavelength. The ratio of monomer to excimer contributions was found to be dependent on the emission wavelength, but was not affected by polymer concentration. Both monomer and excimer fluorescence lifetimes as well as excimer intensity increase with increasing emission wavelength. An accompanying decrease in monomer contribution is also observed is solution in comparison with that in solid films.     

Morphological studies of elongated PMMA by excimer formation

The technique of excimer fluorescence has been employed to study the orientational structure of poly (methyl methacrylate) (PMMA). The PMMA films used contain a small amount of naphthalene‐labeled PMMA, and were uniaxially stretched to various elongation at 80°C. The results show that the fluorescence intensity ratio of excimer to monomer, I_E/I_M , increases with the elongation ratio. The increase of excimer forming sites in the system after drawing is attributed to the orientation of both the chain segments and side groups along the drawing direction. The orientation leads to highly dense packing of the PMMA molecules. The conclusion drawn from excimer fluorescence is in agreement with those from other techniques. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1869–1872, 2000     

Time-resolved fluorescence of excimer-forming polymers in solution

The kinetics of excited dimer (excimer) formation in small molecules, and in excimer-forming polymers, is discussed. The use of time-resolved fluorescence to study molecular order, and heterogeneity, segmental motion and energy migration in synthetic polymers in solution is described with respect to p-phenylene diacrylic acid, a cross-linkable commercial polymer, and copolymers of methyl methacrylate and 1-vinyl naphthalene, respectively.     

Synthesis and properties of some fluorescent 1,8‐naphthalimide derivatives and their copolymers with methyl methacrylate

Six new fluorescent derivatives of 1,8‐naphthalimide were synthesized. Three were dyes, and three were fluorescent whitening agents (FWAs) containing a tetramethylpiperidine (TMP) stabilizer fragment. The FWAs were obtained under phase‐transfer catalysis conditions. Five of the compounds were copolymerized with methyl methacrylate, so copolymers with an intense color and/or fluorescence stable against solvents were obtained. The chemical bonding of the synthesized monomers in the polymers was confirmed spectrophotometrically. The participation of the monomer compounds did not significantly affect the process of copolymerization or the molecular masses of the obtained copolymers. The quantity of chemically bonded naphthalimide monomer in the copolymers was determined to be over 60%. The spectral properties of the compounds and their photostability in solution and in the copolymers were studied. The influence of the compounds on the photostability of the copolymers was determined. The compounds, especially those containing a stabilizer (TMP) fragment in their molecules, showed a positive stabilizing effect on the photodegradation of poly(methyl methacrylate). Polyamide fabrics with 2‐allyl‐6‐hydrazino‐benzo[de]isoquinoline‐1,3‐dione, 2‐allyl‐6‐(2‐amino‐ethylamino)‐benzo[de]isoquinoline‐1,3‐dione, and 2‐chloro‐N′‐(2‐methyl)‐1,3‐dioxo‐2,3‐dihydro‐1H‐benzo[de] isoquinoline‐6‐yl) acetohydrazide were dyed, and materials with an intense yellow color and fluorescence were obtained. Cotton fabrics were whitened with 2‐(2,2,6,6‐tetramethyl‐piperidin‐4‐yl)‐6‐methoxy‐benzo[de]isoquinoline‐1,3‐dione, 2‐(2,2,6,6‐tetramethyl‐piperidin‐4‐yl)‐6‐allyloxybenzo[de]isoquinoline‐1, 3‐dione, and 2‐[2‐(2,2,6,6‐tetramethyl‐piperidin‐4‐yl)‐1,3‐dioxo‐2,3‐dihidro‐1H benzo [de]isoquinoline‐6‐oxy]ethyl‐2‐methacrylate, and materials with bright whiteness and intense bluish fluorescence were obtained. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of photo- and pH-responsive composite nanoparticles using a two-step controlled radical polymerization method

We present a versatile synthetic method for photo- and pH-sensitive composite nanoparticles using a combined use of reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP). Crosslinked nanoparticles of a random copolymer composed of methyl methacrylate (MMA), 4-vinylbenzyl chloride (VBC) and divinylbenzene (DVB) were first synthesized using RAFT miniemulsion polymerization in aqueous solution. This was followed by solvent exchange through extraction and dialysis that allowed the nanoparticles to be transferred to and highly swollen in an organic solvent (anisole or THF). By dissolving a monomer of a stimuli-responsive polymer in the solution, subsequent ATRP grafting polymerization could be initiated by halide groups on the swollen nanoparticle, resulting in larger composite nanoparticles. Photosensitive poly(1-pyrenylmethyl methacrylate) (PPyMA) and pH-sensitive poly(dimethylaminoethyl methacrylate) (PDMAEMA) were incorporated in the composite nanoparticles, and their photo- and pH-responsive behaviors were investigated. With this method, monomers soluble in organic solvents can be used in conjunction with emulsion polymerization in aqueous solution to design functional composite nanoparticles.     

Radical copolymerization of sulphur dioxide and styrene: 4. Intramolecular excimer formation in poly(styrene sulphone)s

Intramolecular excimer formation in poly(styrene sulphone)s with various compositions has been investigated based on the characteristic monomer sequence distributions which were determined experimentally. The fluorescence spectra of the poly(styrene sulphone)s show two emission bands at 285 nm and 330 nm as for polystyrene, corresponding to the monomer and the excimer bands, respectively. The ratio of the excimer to the monomer emission intensities (I_e/I_m) is linearly correlated with the mole fraction of styrene. This observation is a consequence of the characteristic sequence distributions in poly(styrene sulphone)s. containing a very small fraction of SMS units (S = SO₂; M = styrene). The efficiency of excimer formation in poly(styrene sulphone)s with regular styrene sequences, e.g. dyad sequence only, was calculated from the sequence distribution and empirical I_e/I_m. It is concluded that the excimer formation in poly(styrene sulphone)s is very efficient. Energy migration along the copolymer chain was also demonstrated by measuring the degree of polarization as a function of copolymer composition. The efficient excimer formation and the depolarization in poly(styrene sulphone)s suggest that the SO₂ unit in poly(styrene sulphone)s does not act as a barrier or trap to energy migration unlike the methyl methacrylate unit.     

Polymerization of vinyl monomers initiated by zwitterionic polymer in aqueous solution

The polymerization of vinyl monomers, mainly styrene and methyl methacrylate, initiated by zwitterionic poly[3-dimethyl(methacryloyloxy-ethyl)ammonium propane sulfonate], [poly(DMAPS)], in aqueous solution was studied under vacuum at 85°C. An initiation mechanism involving hydrogen atom transfer is proposed. The effects of the efficiency of grafting. pH, water content and betaine polymer content on the polymerization were investigated. The conversion of vinyl monomers in poly(DMAPS) is lower than that in poly [3-dimethyl(acryloyloxyethyl)ammonium propane sulfonate], which may be due to steric hindrance of the methyl group on the α-carbon of the former.     

Solution and solid‐state blend compatibility of poly(vinyl alcohol) and poly(methyl methacrylate)

The blend miscibility of poly(vinyl alcohol) and poly(methyl methacrylate) in N,N′‐dimethylformamide solution was investigated by viscosity, density, ultrasonic velocity, refractive index, and UV and fluorescence spectra studies. Differential scanning calorimetry and scanning electron microscopy were used to confirm the blend miscibility in the solid state. Blends were compatible when the concentration of poly(vinyl alcohol) was greater than 60 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2415–2421, 2006     

Photophysical studies of copolymers of N‐vinylcarbazole

The absorption, fluorescence excitation and emission spectroscopy, and time‐dependent spectrofluorimetry have been used to study the photophysics of copolymers of N‐vinylcarbazole with different monomers like vinyl acetate, methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate in dichloromethane. In all the copolymers and at different N‐vinylcarbazole content, the absorption spectra reflect only the monomer carbazole units. The two kinds of excited monomer species of N‐vinylcarbazole are present in S₁ state. Short‐lived (～3 ns) excited monomer decays forming low energy excimer obtained by the complete overlap of the excited carbazole monomer. The long‐lived excited monomer (～8 ns) decays to ground state without formation of any excimer. The high energy excimer is relatively short‐lived and is formed by the partial overlap of the carbazole units. The presence of bulky group in the copolymer chain hinders the formation of excimers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 372–380, 2006     

Synthesis and properties of new poly(amide‐imide)s based on 1,3‐bis[4,4'‐(trimellitimido) phenoxy] propane and aromatic diamines

Six new poly(amide‐imide)s 8a–f containing trimethylene moiety in the main chain were synthesized by the polycondensation reactions of 1,3‐bis[4,4'‐(trimellitimido) phenoxy] propane 6 with six different aromatic diamines 7a–f in a medium constituting N‐methyl‐2‐pyrrolidone, triphenylphosphite, CaCl₂, and pyridine as condensing agents. The polycondensation reaction produced a series of novel poly(amide‐imide)s 8a–f in high yields with inherent viscosities between 0.35 and 0.63 dL/g. The resulting poly(amide‐imide)s were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), solubility tests, and FTIR spectroscopy. 1,3‐Bis[4,4'‐(trimellitimido) phenoxy] propane 6 as a new monomer containing trimethylene moiety was synthesized using a three‐step reaction. At first 1,3‐bis[4,4'‐nitrophenoxy] propane 3 was prepared by the reaction of 4‐nitrophenol 1 with 1,3‐dibromo propane 2 in DMF solution . Then, dinitro 3 was reduced to 1,3‐bis[4,4'‐aminophenoxy] propane 4 by using a solution of sodium sulfite in ethanol. Finally, 1,3‐bis[4,4'‐(trimellitimido) phenoxy] propane 6 was prepared by the reaction of one equivalent diamine 4 with two equivalents of trimellitic anhydride 5 in a mixture of acetic acid‐pyridine (3 : 2). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Miscibility of DMPC‐TMPC copolycarbonate/SMMA copolymer blends and their interaction energies of binary pairs involved in blends

The isothermal miscibility map and phase‐separation temperatures caused by lower critical solution temperature‐type phase behavior for blends of poly[2,2,‐propane‐bis{4‐(2‐methyl phenyl)} carbonate]‐poly[2,2,‐propane‐bis{4‐(2,6‐dimethyl phenyl)} carbonate] (DMPC‐TMPC) with poly[(styrene)‐co‐(methyl methacrylate)] (SMMA) copolymers have been determined. SMMA copolymers containing equal to or less than 37 wt% MMA formed miscible blends with DMPC‐TMPC copolycarbonates containing equal to or more than 60 wt% TMPC. The observed phase‐separation temperatures indicate that the miscibility decreases as the DMPC content in DMPC‐TMPC increases, while addition of MMA to the styrene initially increases miscibility with DMPC‐TMPC but ultimately leads to immiscibility. The binary interaction energies involved in these blends were calculated from the phase boundaries using the lattice‐fluid theory combined with the binary interaction model. The spinodal temperatures predicted from the lattice‐fluid theory using the calculated interaction energies are similar to the experimental phase‐separation temperatures. Copyright © 2004 Society of Chemical Industry     

Ablation of poly(2-hydroxyethyl methacrylate) by 193-nm excimer laser radiation

Data on the ablation of poly(2-hydroxyethyl methacrylate) (PHEMA) by 193-nm radiation pulses, produced by an ArF excimer laser, are presented for the first time and are compared with the data for poly(methyl methacrylate) (PMMA). The ablation rate of PHEMA is lower than that of PMMA and some possible explanations are advanced. The other features of the etch curves are similar and confirm a predicted ablative behavior of the addition polymers susceptible to depolymerization. Geometric aspects of the ablated polymer's surface, and the influence of inhomogeneities in the material, are also presented and discussed.     

Photocurrent in and miscibility of poly(N-vinylcarbazole)/poly(methyl methacrylate) blends

Summary Steady-state photocurrent in poly(N-vinylcarbazole)(PVCz) (26,48 wt%)/poly(methyl methacrylate)(PMMA) blends is for the first time measured. The PVCz(26,48 wt%)/PMMA blends showed almost the same carrier-generation efficiencies at electric fields higher than 1 × 10⁵ V · cm⁻¹. The results are explained by high miscibility of the PVCz(26,48 wt%)/PMMA blends, suggesting the existence of PVCz chains in continous PMMA-rich phase in the phase-separated structure. The miscibility is also evaluated by means of excimer fluorescence of PVCz in these blends and fluorescence microscopy. Received: 26 December 2000/Revised version: 16 January 2001/Accepted: 19 January 2001     

Molecular weight effect on swelling of polymer gels in homopolymer solutions: a fluorescence study

A novel technique based on in situ steady state fluorescence measurements is introduced for studying swelling processes of gels formed by free radical crosslinking copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) in homopolymer solutions. Gels were prepared at 55±2 °C for various EGDM contents. After drying these gels, swelling experiments were performed in chloroform solution of anthracene labeled poly(methyl methacrylate) (An-PMMA) in various molecular weights at room temperature by real time monitoring of anthracene fluorescence intensity. Anthracene labeled PMMA chains having various molecular weights were prepared by atom transfer radical polymerization at 90 °C. During the swelling experiments, it was observed that anthracene emission intensities increased due to trapping of An-PMMA chains into the gel as the swelling time is increased. The trapping of An-PMMA chains in swollen gel, increase by obeying parabolic law in time. Penetration time constant, τ of PMMA chains were measured and found to be increased as the crosslinker density of gel is increased. It is observed that τ values are much higher for high molecular weight An-PMMA chains than low molecular weight chains in all gel samples.     

Miscibility of poly(2-chloroethyl methacrylate) with various polymethacrylates

The miscibility behavior of poly(2-chloroethyl methacrylate) (PCEMA) with various polymethacrylates was investigated by differential scanning calorimetry. PCEMA is miscible with poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(tetrahydrofurfuryl methacrylate) (PTHFMA), but is immiscible with poly(n-propyl methacrylate), poly(isopropyl methacrylate), poly(n-butyl methacrylate), and poly(cyclohexyl methacrylate). PCEMA/PEMA blends showed lower critical solution temperature (LCST) behavior but PCEMA/PMMA and PCEMA/PTHFMA blends degraded before phase separation could be induced. The miscibility behavior of PCEMA is similar to that of a chlorinated polymer.     

Preparation and structure of crosslinked poly(methyl methacrylate-co-1,3-bis-(methacryloxymethyl)-1,1,3,3-tetramethyl disiloxane)

Summary An investigation is presented of the swelling, thermal and morphological characteristics of copolymers of methyl methacrylate and 1,3-bis-(methacryloxymethyl)-1,1,3,3-tetramethyl disiloxane. These materials were prepared by copolymerization/ crosslinking of the two monomers by gamma irradiation. Studies were performed on copolymers with mole fraction of the silicon-containing monomer ranging from 0.09 to 0.42.     

Molecular weight dependence of excimer formation of poly(α-methylstyrene)

Summary The molecular weight dependence of the fluorescence properties of poly (-methylstyrene) (PMS) was investigated in cyclohexane solution. The ratio of excimer to monomer fluorescence intensity increases with increasing degree of polymerization up to 50 after which the plateau value does not change. This molecular weight dependence of the excimer formation appears to be related to that of the local motion of PMS in fluid solution.