Fluorescence random copolymers

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... 

With the single exception of PS-B, the PS homopolymers are more photostable than the copolymers. Among the random copolymers, the quantum yield for scission Increases as the proportion of S-unlts decreases. The least stable copolymers are those in which the S-unlts are separated by one or more MMA-units exclmer fluorescence Is not observed In these copolymers (1). As the ratio of exclmer fluorescence to fluorescence Increases, the quantum yield for scission decreases. Wherever a migrating singlet exclton Is trapped at an exclmer site. It Is less likely to contribute to the scission process. 

Dias FB, Knaapila M, Monkman AP, Burrows HD (2006) Fast and slow time regimes of fluorescence quenching in conjugated polyfluorene-fluorenone random copolymers The role of exciton hopping and dexter transfer along the polymer backbone. Macromolecules 39(4) 1598—1606... 

Analysis of the fluorescence decay curves in water indicated that the intracoil process is static and that anthryl aggregation induces non-exponentiality in the fluorescence decay associated with a dynamic equilibrium between the singlet diphenyl-anthracene and a non-fluorescent dimer state. Further evidence was also presented to show that these polymers self-organise into hydrophobic and hydrophilic regions Energy migration in alternative and random copolymers of 2-vinylnaphthalene and methyl methacrylat methacrylic acid... 

PolyCACN) has a rigid chain structure yet can form excimers with alternate units along the chain (8), or by stacking in a helical conformation. Excimer formation has been reported for alternate copolymers of ACN with styrene (9) and for ACN with maleic anhydride CIO). The situation is different for 2-vinylnaphthalene since alternating copolymers of 2VN with methyl methacrylate or methacrylic acid did not form excimers, yet random copolymers of the same systems showed excimer fluorescence Cll). Only random copolymers of ACN were prepared in this work. 

For comparison with the alternating copolymer we synthesized a randcm polymer of 2-VN and MA containing ca. 10 mol of 2-VN (higher naphthyl contents did not dissolve In basic H O). Solubilization by this copolymer demonstrates 1) a much lower sensitization efficiency than the alternating copolymer, 2) no spectral shift between directly excited and sensitized AnOH, and 3) In the absense of AnOH a clearly discernible exclmer component In the fluorescence (see Fig. 7). While comparison of the alternating and random copolymer Is dangerous because of the different naphthyl contents, these results do Imply that 1) the AnOH Is not preferentially associated with the naphthyl moieties In the random copolymer, and 2) the red-shift observed In the sensitized AnOH fluorescence for P(2VN-alt-MA) is the result of naphthalene - anthryl Interactions. 

Mundra, M. K., Ellison, C. J., Behhng, R. E., and Torkelson, J. M., Confinement, composition and spin coating effects on the glass transition and stress relaxation of thin films of polystyrene and styrene containing random copolymers sensing by intrinsic fluorescence. Polymer, 47, 7747-7759 (2006). 

Random copolymer. Figures 5 and 6 show the absorption and fluorescence spectra of the random copolymers consisting of (A) and (D) units. The absorption peak shifts proportionally to the ratio of (A) and (D), while the absorption edge shifts less than the peak. Similar shifts in absorption and fluorescence spectra were observed in the copolymers of A /B, and A/C. 

ROMP copolymers were also explored to disperse a platinum chromophore in a solvent in which the parent chromophore was insoluble. Slugovc et al. [75] reported the synthesis of amphiphilic triblock random copolymers containing a blue fluorescent host and a red phosphorescent guest. Deep red phosphorescence, stemming from the platinum complex used as guest component, was observed with a large Stokes shift of about 260 nm. Moreover, considerable phosphorescent quantum yields were demonstrated thanks to a suppression of the self-aggregation of the platinum complex. In a further work, the same... 

Hydrophobic associations in random copolymers of AMPS and iV-d ecylmethacrylamide (DodMAm) were investigated by viscometry, QELS, capillary electrophoresis (CE), NMR relaxation, and various fluorescence techniques (24,48), For fluorescence studies, the polymers that are singly-labeled with pyrene or naphthalene or doubly-labeled with pyrene and naphthalene (Chart 2) were employed (48). In this section, the self-association behavior of AMPS-DodMAm co lymers in water will be discussed with a focus on intra- and interpolymer self-associations as a function of the DodMAm content (/bod) in Ae copolymer. 

Yusa et al. showed that the random copolymer of 11-aminododecanoic acid and sodium 2-(acrylamidopropane-sulfonate) forms unimolecular micelles in water at pH < 5. At pH > 5 the unimolecular micelle conformation is transformed into an open-chain conformation. P3rrene fluorescence measurements showed that the transformation is completed in less than 6 min (dead time of the measurements). 

In addition, there have been a number of studies of the steady state fluorescence properties of styrene random copolymers in dilute solution as a function of copol3nner composition [57-60] In these studies, the conclusion that energy migration is important in PS has generally been reached based on correlations between the ratio of excimer-to-monomer fluorescence and various parameters that describe copolymer composition ... 

Zhou et al. [177] use a random copolymer of tetrahydropyranyl methacrylate (THPMA) and methyl methacrylate (MMA) polymer doped with BSB-S2 as the PAG for microfabrication. At the laser focal spot, the THPMA groups were converted to carboxylic acid groups due to photogenerated acid-induced ester cleavage reactions, and were therefore rendered soluble in aqueous base developer. Figure 45 shows the 3D microstructure produced by this method. By two-photon fluorescence imaging, it was found that the buried channels are open and a continuous connection was made between the two cavities. 

Fluorescence techniques are particularly useful to probe a short-dimensional structure. The formation of unimer micelles by the random copolymers of AMPS and 1-NpMAm shown in Scheme 2 [poly(A/l-Np(x)) where x stands for the mole percentage content of the 1-NpMAm unit in the copolymer] can easily be monitored by the fluorescence emitted by the 1-Np unit in the copolymers [25]. As the 1-Np content increases, fluorescence from monomeric 1-Np (337 nm) decreases and, in turn, excimer fluorescence (390 nm) increases. The copolymers emit almost entirely excimer fluorescence when the 1-Np content is higher than 41 mol%. As can be seen in Fig. 6, the ratio... 

---