M.G. Krakovyak

Polarized luminescence in the investigation of the molecular-weight dependence of the rotational motion of macromolecules in solution☆

Abstract A study was made of the effect of molecular weight on the intramolecular mobility of macromolecules in solution for acrylic polymers containing luminescent markers (LM) situated in the main chain or the side groups of the macromolecules. The relations between relaxation times and mol. wt. τ ω ( M ) were investigated for non-ionized polymethacrylic acid in water with LM of different structures in the range M 2700–330,000. The τ ω ( M ) curve revealed the transition from the region of large M values ( M > 10 4 ), where τ ω is not a function of M to the region of low M ( M 4 ) where τ ω is reduced with decreasing M . In the range of low M the τ ω (M) relationship was elucidated in terms of the theory of Gaussian sub-chains for a finite number of segments. It is shown that with low M the equation 1/ τ ω whole +1/ τ intra is satisfied, i.e. the mobility of the macromolecules may be represented in a first approximation as the sum of the contributions of the rotation of the macromolecule as a whole 1/ τ whole and of the intramolecular mobility 1/ τ intra .

Preparation of polymers with luminescent markers

POLYMERS tO which chromophore groups have been covalently added are most frequently used for studying certain properties of natural and synthetic macromolecules and the mechanism of their formation [1-4]. The relaxation behaviour of polymers with luminescent groups may be studied by the polarized luminescence method. The latter is repeatedly used with success in studying rapid relaxation processes when the periods of relaxation and luminescence are comparable; moreover it enables us to study the intramolecular motion of macromolecules in solution and in the mass. The advantages of the method include the possibility of experiments in water and other polar solvents; this along with the high sensitivity of the method facilitates work with low concentrations of the polymer in solution. The polarized luminescence method [1, 4] involves the use of luminescent markers covalently added to the macromolecules and possessing certain optical properties. The number of these specially added groups must be sufficient for purposes of spectral analysis and small enough to prevent distortion of the properties of the macromolecules. Several methods of preparing macromolecules with chemically added luminescent groups have been described [2, 5], but these are mainly applicable to polymers that have NH bonds. Our aim was to develop a convenient and general method of adding luminescent groups to polymers containing carboxyl groups. In a previous study [4] we prepared polyacrylic and polymethacrylic acids with covalently added luminescent groups. However the method used for their preparation involves polymer analogue conversions of the corresponding polyacryloyl chlorides, and this limits its usefulness. The chemical addition of luminescent groups to polymers containing carboxyl groups may be realized through specially selected aliphatic diazo compounds (diazoalkanes) interacting with COOH groups of the polymer. The reaction of diazoalkanes with earboxylic acids proceeds by the scheme [6]

Interaction of protein molecules with a linear polyelectrolyte in solution

The polarized luminescence method was used to analyze changes in the synamic properties of protein (lysozyme) molecules interacting with polymer chains of polymethacrylic acid in water and in water-salt solutions and participating in processes of complex formation. The irregular mode of distribution of protein molecules between polyelectrolyte chains is shown: some parts of the polymethacrylic acid are compactly filled with protein, while other parts remain unfilled. Conditions of protein-polyelectrolyte complex formation have been determined ,as well as structural particularities making for greater stability of these complexes.

Polarized luminescence as used for analyses of high frequency twisting vibrations in macromolecules

Abstract Theoretical correlations for degrees of luminescence polarization have been analysed for different models of inhibited internal rotation and twisting vibrations. It was found that average amplitudes can be determined for high-frequency twisting vibrations (HTV) in the main chain and in side radicals by means of the polarized luminescence of “labelled” macromolecules with luminescing groups (LG). The HTV amplitudes were found by comparing theoretical considerations with experimental findings. The HTV amplitudes depend on interactions between the anthracene nucleus and the macromolecular units nearest to the LG, and likewise on the length and flexibility of the side radical containing the LG. Matters relating to these correlations are discussed.

The Friedel-Krafts reaction of anthryl groups and phenyl containing polymers☆

A method for the addition of a specific amount of anthryl groups to phenyl containing polymers (e.g. of styrene, α-methylstyrene, polyvinylbenzyl- and polypropenylbenzyl ethers), based on the Friedel-Krafts reaction has been developed. It makes use of reagents of the type A-CH(R)-X (in which A=9-anthryl, R=H or CH3, X=Cl or OH) and of SnCl4 and BF3·O(C2H5)2 as catalysts at 25 to −78°C. The solvents used are inert with respect to the alkylating agents (methylene chloride, o-dichlorobenzene).

A study of the mobility of main and side chains of macromolecules by polarized luminescence

On the basis of data obtained by polarized luminescence with PMMA having luminescent groups (anthracene nuclei) introduced in tracer quantities in the main chain, in side chains with various structures or at the end of the macromolecule, the intramolecular mobility of “labelled” fragments of the polymer chain has been analysed theoretically. It has been established that, in addition to the high frequency torsional vibrational motion of small amplitude with times τh.f, which are much less than the lifetime of the excited state τθ of the luminescent groups, comparatively slow low frequency motions (rotational isomerization or a combination of jumps and vibrations) with τ1.f  τ1.g ≈ τgq and jumps of considerable amplitude are an inherent property of the side chains and end segments of macromolecules. Within the framework of a simple model of the cooperatice combined movement of the main and side chains of the polymer, τ1.f has been assessed as a function of the chemical structure of the “labelled” side chains. The results obtained may be used in analysing the effecś of the intramolecular mobility of macromolecules on their reactivity.

Synthesis routes for phenyl containing polymers with anthracene groups

Abstract Polarized luminescence was used to study the relaxation characteristics of phenyl containing polymers (PCP) which were produced with luminescence labels on the anthracene structure; these are in special parts of the macromolecules (the branch groups, the main chain, or at the chain ends). The methods for producing PCP with anthracene groups are based on free radical polymerization in which anthracene containing monomers or chain terminating agents participate.

Quantitative determination of carboxyl groups when contained in low proportions in polymers

Abstract A method was developed for the quantitative determination of carboxyl groups when contained in low proportions in polymers (0.1–0.002 mol.%); the method is based on exhaustive esterification with 9-anthryldiazomethane followed by spectrophotometric determination of 9-anthylmethylcarboxylate groups in the polymer.

Intermolecular interactions of stereospecific sequences in polymethyl methacrylates

Abstract Intermolecular interactions of sterically complementary PMMA macromolecules having differing stereochemical compositions have been investigated in various solvents, using the method of polarized luminescence. The introductions of comonomer in small (label) amounts (0·1%) into the growing PMMA chain during the copolymerization changes the local stereochemical structure of the polymer. These changes depend on the comonomer structure.

Kinetic flexibility and structural transformations of polysaccharide macromolecules

Structure formation has been studied in polyuronide solutions, using polarized luminescence. It has been shown that intramolecular hydrogen bonds, with participation of COOH groups or ionically coordinated bonds with participation of COO− groups and Ca2+ ions, play an essential role in the formation of an intramacromolecular structure. The substitution of carboxyl by methylcarboxylate groups prevents structure formation. In conditions promoting intramacromolecular hydrogen bonds, the polyuronides have a kinetic flexibility, comparable with that of PMMA.