Copolymer fluorescence

Acrylic copolymers Fluorescence, ATR Structure and H bonding of dissolved water in polymers 1069... 

Fig. 15.20 Stretched exponential analysis of PF/FLq 25 copolymer fluorescence decay, with emission collected at 415 nm. Reproduced with permission from Ref. [91], Copyright 2006, the American Chemical Society...

Micellar structure has been a subject of much discussion [104]. Early proposals for spherical [159] and lamellar [160] micelles may both have merit. A schematic of a spherical micelle and a unilamellar vesicle is shown in Fig. Xni-11. In addition to the most common spherical micelles, scattering and microscopy experiments have shown the existence of rodlike [161, 162], disklike [163], threadlike [132] and even quadmple-helix [164] structures. Lattice models (see Fig. XIII-12) by Leermakers and Scheutjens have confirmed and characterized the properties of spherical and membrane like micelles [165]. Similar analyses exist for micelles formed by diblock copolymers in a selective solvent [166]. Other shapes proposed include ellipsoidal [167] and a sphere-to-cylinder transition [168]. Fluorescence depolarization and NMR studies both point to a rather fluid micellar core consistent with the disorder implied by Fig. Xm-12. 

An interesting application of this reaction was the use of macro-molecular anhydrides, namely, styrene-maleic anhydride or vinyl acetate-maleic anhydride copolymers in the presence of perchloric acid as catalyst, these copolymers acylate mesityl oxide or d rpnone to macromolecular pyrylium salts which, with aryl substituents, are fluorescent.No crystalline products could be obtained from succinic anhydride because of the solubility and ease of decarboxylation. 

The presence of a critical St content in ASt-x can also be seen in fluorescence spectra [29], This copolymer in aqueous solution shows an excimer emission peaking at 325 nra. As shown in Fig. 8, the intensity of the excimer emission increases, while the monomer emission decreases, with increasing St content. Eventually the excimer dominates the monomer emission at an St content of 72 mol%. The excimer emission becomes apparent at an St content of about 50 mol%, which agrees with the critical St content estimated by viscometry and NMR spectroscopy. The existence of the critical St content suggests the hydro-phobic self-aggregation to be a cooperative process. 

Figure 11 shows Stern-Volmer plots for fluorescence quenching of the amphiphilic cationic copolymer QPh-x [74]. The quenching of QPh-x with MV2+ is expected to be much less effective than that of APh-x. The quenching data for the QPh-x system are presented in Table 3. For comparison, the data for a related... 

Similar data were reported by Turro et al., [62,63] who synthesized a copolymer of AA with 1.5 mol% of 2-[4-(l-pyrene)butanoyl]aminopropenoic acid, 19 and studied the fluorescence quenching with Tl +, Cu2+, and 1 ions in aqueous solution. 

Fig. 13. Fluorescence spectra of copolymers of acenaphtylene with phenylacetylene. Content of phenylacetylene blocks (1) 14 mol-%, (2) 20 mole-%, (3) 35 mole-%, (4) 48 mole-% (5) 94 mole-%. Spectra are taken in benzene solution C= 10"4 mol/1. excitation = 324 m...

In 2000, the first example of ELP diblock copolymers for reversible stimulus-responsive self-assembly of nanoparticles was reported and their potential use in controlled delivery and release was suggested [87]. Later, these type of diblock copolypeptides were also covalently crossUnked through disulfide bond formation after self-assembly into micellar nanoparticles. In addition, the encapsulation of l-anilinonaphthalene-8-sulfonic acid, a hydrophobic fluorescent dye that fluoresces in hydrophobic enviromnent, was used to investigate the capacity of the micelle for hydrophobic drugs [88]. Fujita et al. replaced the hydrophilic ELP block by a polyaspartic acid chain (D ). They created a set of block copolymers with varying... 

Quantum yields and lifetimes of emission (fluorescence) as well as other principal rates of deactivation have been measured on 2-hydroxy benzophenone and 2-hydroxyphenyl benzotriazole derivatives. Polymerizable UV screening agents have been prepared and copolymerized with acrylics in order to obtain transparent films containing nonfugitive UV screening agents. Preliminary results of studies of photodegradation on these copolymers are also reported here. 

Photophysical Processes in Pol,y(ethy1eneterephthalate-co-4,4 -biphenyldicarboxyl ate) (PET-co-4,4 -BPDC). The absorption and luminescence properties of PET are summarized above. At room temperature the absorption spectrum of PET-co-4,4 -BPDC copolymers, with concentrations of 4,4 -BPDC ranging from 0.5 -5.0 mole percent, showed UV absorption spectra similar to that of PET in HFIP. The corrected fluorescence spectra of the copolymers in HFIP exhibited excitation maxima at 255 and 290 nm. The emission spectrum displayed emission from the terephthalate portion of the polymer, when excited by 255 nm radiation, and emission from the 4,4 -biphenyldicarboxylate portion of the polymer when excited with 290 nm radiation. 

Examination of the corrected room temperature fluorescence properties of PET yarns revealed an excitation maximum at 342 nm with a corresponding emission maximum at 388 nm. At 77°K, in the uncorrected mode, the fluorescence spectra of PET yarns exhibited a structured excitation having maxima at 342 and 360 nm and a shoulder at 320 nm. At 77°K, PET yarns displayed a structured emission with maxima at 368 and 388 nm. As in solution, the copolymer yarns showed both fluorescence from the terephthalate portion of the polymer and the 4,4 -biphenyldicarboxyl ate portion of the polymer. Excitation at 342 nm produced an emission band centered at 388 nm. This excitation and emission correspond to the PET homopolymer emission. Excitation with about 325 nm light produced an emission with a maximum near 348 nm from the 4,4 -biphenyldicarboxyl ate portions of the polymer. 

As the concentration of 4,4 -BPDC increases, an increase in the intensity of the band at 289.5 nm was observed. This is the result in the increased intensity of the A - lL- transition of the 4,4 -BPDC in this region. In dilute HFIP solutions the copolymers show a fluorescent emission in the 326 - 338 nm range when excited with 255 nm radiation. This emission corresponds to emission from the terephthalate units of the copolymer. 

In the yarns, the fluorescence of the 4,4 -biphenyldicarboxy-late unit is distinct and predominate both at 298 and 77°K. Examination of the phosphorescence spectra of the PET and PET-co-4,41-BPDC yarns revealed three emission maxima. In the PET homopolymer excitation with 310 nm radiation produced an emission at 452 nm from the terephthalate chromophore. In the copolymers excitation with either 305 or 310 nm radiation produced emission spectra with distinct maxima at 480 and 515 nm (t 1.2 sec), and a shoulder near 452 nm (t = 1.2 sec). The maxima in the phosphorescence spectra were assigned as emission from the 4,4 -biphenyldicarboxylate units of the copolymer. The observed emissions are bathochromatically shifted from the emission of 4,4 -BPDC in a glassed solvent. This is supported by the observed emissions from solid 4,4 -BPDC at 520 and 560 nm (t =. 3 sec) when excited with 340 or 356 nm radiation. 

The observed luminescence properties of the copolymer yarns can be easily explained if an energy transfer mechanism is assumed to be operating (Figure 7). Triplet-triplet energy transfer from the terephthalate units to the 4,4 -biphenyl -dicarboxyl ate units explains both the dual fluorescent/phospho-rescent emissions from the 4,4 -biphenyldicarboxyl ate units as well as the quenched phosphorescence from the terephthalate units. 

On the other hand, the exposed copolymer yarn containing 4.0 mole percent 4,4 -BPDC still exhibits the normal terephthalate fluorescence (388 nm emission) as the major band in the emission spectrum when excited with 342 nm energy. 

The corrected excitation and fluorescence spectra of PET-4,4 -SD copolymers in HFIP solution or as yarns were identical to the spectra of PET homopolymer. The uncorrected phosphore-sence excitation and emission spectra of PET-4,4 -SD copolymer yarns were also identical to that of the PET homopolymer yarn. 

Fluorescence Analysis of Irradiated PET and PET-4,41-SD Yarns. As we noted above, the fluorescence emission at 460 nm in irradiated PET polymer has been attributed to the hydroxyterephthaloyl component (2). The fluorescence spectra of irradiated (100 hours) PET homopolymer yarns and PET-4,4 -SD copolymer yarns are identical and agree with that obtained by Day and Wiles for PET film (2). 

TGA, iodometric, mid-IR, luminescence (fluorescence and phosphorescence) and colour formation (yellowness index according to standard method ASTM 1925) were all employed in a study of aspects of the thermal degradation of EVA copolymers [67], Figure 23 compares a set of spectra from the luminescence analysis reported in this work. In the initial spectra (Figure 23(a)) of the EVA copolymer, two excitation maxima at 237 and 283 nm are observed, which both give rise to one emission spectrum with a maximum at 366 nm weak shoulders... 

Second, some organisms are able to incorporate longer pendent chains yielding another class of PHA medium chain length PHA, poly(HAMCL). Poly (HAmcl) is specifically accumulated by fluorescent pseudomonads. When aliphatic hydrocarbons like n-alkane, n-alkanoate, or n-alkanol serve as feedstocks for Pseudomonas oleovorans the resulting PHA is a random copolymer... 

Figure 4. Synthesis of an indicator dye for amines which exhibits methacrylate groups for preparation of copolymers. The dye shows a reversible change in fluorescence from green to blue upon interaction with amphetamine.

---