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Serrano, Berna; Baselga, Juan; Bravo, Julio; Mikeš, František; Sesé, Luis M.; Esteban, Irène; Piérola, Inés F.

doi:10.1023/a:1009439024969

Cited by 18 publications

(16 citation statements)

References 7 publications

(2 reference statements)

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“…Other methods are based on the measurement of the nonradiative energy transfer that depends on the distance between both fluorophores (guest in different domain), and therefore on the interpenetrating in the interface between the individual domain [10][11][12]. Epifluorescence microscopy (EFM) and fluorescence microspectroscopy were also employed to study the domains incompatible in blends with poly(vinyl acetate) [11,13,14]. However, the more sensitive technique is that the smaller domain it can detect.…”

Section: Introductionmentioning

confidence: 99%

Effect of the morphology of two phase polymer blends on glass transition temperature

Serrano

Piérola

Bravo

et al. 2003

Journal of Materials Processing Technology

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Blends of poly(cyclohexylmethacrylate), PChMA, with poly(vinylacetate), PVAc, were prepared by casting THF and chloroform solutions. A calorimetric and morphologic study was performed. Differential scanning calorimetry investigations of the blends show two glass transition temperature that give evidence of inmiscibility. For polymer less flexible (PChMA) was observed an enhancement of T g by 20 8C approximately in blends of PVAc-rich composition. Epifluorescence microscopy, using PChMA labelled by copolymerization pirenyl-methylmethacrylate, Py, shows also phase separation providing imaging of the distribution of PChMA in the different domains and in the matrix. Blends containing 80% w/w PChMA show a bicontinuous primary morphology suggesting a spinodal phase separation mechanism. The 50 and 20% PChMA samples show morphologies composed of PChMA-rich domains in a matrix composed by PVAc mainly. Blends with domain-matrix morphology present a higher T g than pure homopolymer more rigid (PChMA) due to packing in microphases in matrix of more flexible polymer (PVAc).

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Section: Introductionmentioning

confidence: 99%

Effect of the morphology of two phase polymer blends on glass transition temperature

Serrano

Piérola

Bravo

et al. 2003

Journal of Materials Processing Technology

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“…The microstructure of a film made with a single amorphous polymer is expected to be homogeneous, above a certain length scale. Nevertheless, a single polymer is a polydisperse mixture formed by chains of different length that, in principle, i) may be interpenetrated totally or only to a certain extent, [8][9][10][11][12][13] ii) may have preferential positions with respect to polymerair and support-polymer interfaces, [14][15][16] iii) may have different proportions of liquid-like and solid-like domains, [17][18][19] and that, even, iii) may show partially ordered domains. [20][21][22] Thus, a certain heterogeneous microstructure must be expected even in the simplest polymer system: a single polymer sample in the bulk amorphous state.…”

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confidence: 99%

“…[20][21][22] Thus, a certain heterogeneous microstructure must be expected even in the simplest polymer system: a single polymer sample in the bulk amorphous state. Several models have been proposed for the amorphous polymer state [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] but currently, the most widely accepted considers that it is formed by interpenetrating random coils having unperturbed dimensions, as in θ solvents. 23 Only a few techniques give information on the microstructure of bulk amorphous polymer samples, at the molecular level.…”

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confidence: 99%

“…Time resolved fluorescence measurements, may also provide useful information on the microstructure of polymer samples in bulk. 13,16,17,27 Common fluorescent molecules in non-viscous homogeneous dilute solution and in the absence of excimer or exciplex formation give single exponential decays in the nanosecond time range. Such is the case of 9-anthrylmethylmethacrylate (MMA-An) in dioxane dilute solution which yields a fluorescence lifetime of 4.56 ns, 13 a very close value to that previously reported for the model compound, 9-methylanthracene, 4.6 ns.…”

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confidence: 99%

“…13,16,17,27 Common fluorescent molecules in non-viscous homogeneous dilute solution and in the absence of excimer or exciplex formation give single exponential decays in the nanosecond time range. Such is the case of 9-anthrylmethylmethacrylate (MMA-An) in dioxane dilute solution which yields a fluorescence lifetime of 4.56 ns, 13 a very close value to that previously reported for the model compound, 9-methylanthracene, 4.6 ns. 28 Fitting of the MMA-An emission in dilute solution to a fluorescence lifetime distribution worsens the statistical fitting parameters and the trend of the residuals with respect to fittings with discrete number of exponentials.…”

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Fluorescence Lifetime Distributions of Labeled Amorphous Polymers in Bulk

Serrano¹,

Baselga²,

Piérola³

2002

Polym J

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ABSTRACT:Polystyrene, poly(methylmethacrylate), poly(cyclohexyl methacrylate) and poly(1-butylmethacrylate) were labeled with anthryl groups by copolymerization. Films of labeled polymers as well as blends of them with unlabeled polystyrene samples of different polydispersity and molecular weight, were prepared by solvent casting. The time resolved emission of anthryl groups in those films was measured by Single Photon Counting with front face excitation at the standard 30• incident angle and with much lower incident angles to photoselect chromophores on the polymer-air surface. Fluorescence decays were fitted with bimodal fluorescence lifetime distributions, which were analyzed taking into consideration some polymer characteristics and the compatibility of polymer blends. It was thus concluded that solid-like and liquid-like environments are both in the bulk and in the surface of the film although liquid-like domains are more frequent on the surface than in bulk. Polymer T g determines the position of the two modes and polydispersity justify the broadness of the modes in the fluorescence lifetime distribution. KEY WORDS Fluorescence Lifetime Distribution / Fluorescence Decay / Poly(1-butylmethacrylate) / Poly(methylmethacrylate) / Poly(cyclohexylmethacrylate) / Polystyrene / Steady state or time-resolved fluorescence measurements of chromophores added to polymers as probes or labels can yield valuable information on the structural or dynamic properties of the system. 1 Anthryl groups have been broadly employed as polymer labels due to its well known photophysical behavior as well as to its relatively small size and high fluorescence quantum yield. 2, 3 Nevertheless, it was found 4 that the chain mobility of polystyrene (PS) is slightly reduced by the steric hindrance of the anthryl group with phenyl rings and therefore, minimum proportions of labeling groups must be introduced in the polymer to preserve unmodified the macroscopic polymer characteristics. Fortunately, due to the very high sensitivity of this technique, only very low chromophore concentrations are needed, which does not disturb the system properties. But even such low concentrations still report on its environment and on processes occurring in the nanosecond time range.It was shown 2 for anthracene dissolved in PS that rigidity and dimension of the matrix free volume are related with the vibronic structure of the fluorescence spectrum. The non-radiative deactivation processes, which involve out of plane vibrational modes and intermolecular interactions, are inhibited in polymer matrices. 2 As a consequence of the probe-polymer matrix interaction the fluorescence intensity changes with temperature following and revealing polymer relaxation processes. 5 Matrix effects on the radiationless deactivation of substituted anthracenes were also observed in films of poly(methylmethacrylate) (PMMA) and they were attributed to competing intersystem crossing and very fast internal conversion. 6 For 9-methylanthracene, 7 the radiationless deactivation rate coe...

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Morphology of phase separated blends of poly(cyclohexyl methacrylate) with poly(vinyl acetate)

Serrano

Baselga

Esteban

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:Blends of poly(vinyl acetate) (PVAc) and poly(cyclohexyl methacrylate) (PCHMA) labeled by copoly-merization with 4-methacryloylamine-4�-nitrostilbene (Sb), with (1-pyrenylmethyl)methacrylate (Py) or with 3-(methacryloylamine)propyl-N-carbazole (Cbz), were prepared by casting dilute solutions in tetrahydrofurane (THF) or chloroform onto silanized glass plates. The resulting films were studied by epifluorescence microscopy, microfluorescence spectroscopy, DSC and optical microscopy. Epifluorescence micrography probes the chemical composition of the different regions in phase separated blends, with black areas corresponding to PVAc rich regions and colored areas corresponding to labeled PCHMA rich regions. The technique also visualizes primary and secondary morphologies, which depend on the composition of the polymer blend and on the casting solvent. Mixtures containing 80 wt % PCHMA show, in general, a bicontinuous primary morphology suggesting a spinodal demixing mechanism. Solvent effects are particularly relevant for 50% and 20% PCHMA samples showing morphologies composed of PCHMA rich domains, in a matrix of solvent-dependent compositions. Samples cast from chloroform are more homogeneous and the matrix is always highly fluorescent. In contrast, the domains of samples cast from THF are heterogeneous in size and shape and the matrix is non-fluorescent, being thus formed by nearly pure PVAc. Small voids are formed in the polymer-air interface. They are submicrometric for THF cast films and disappear with annealing at 122°C. For chloroform cast samples they are much less frequent and appear well ordered, forming a mostly hexatic two dimensional network.

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Cited by 18 publications

References 7 publications

Effect of the morphology of two phase polymer blends on glass transition temperature

Effect of the morphology of two phase polymer blends on glass transition temperature

Fluorescence Lifetime Distributions of Labeled Amorphous Polymers in Bulk

Morphology of phase separated blends of poly(cyclohexyl methacrylate) with poly(vinyl acetate)

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