Poly(ortho-vinylbenzophenone)

This article reports the synthesis and free radical polymerization of ortho-vinylbenzophenone. The glass transition temperature T_g of the homopolymer is 136°C. The products synthesized appeared to be atactic and amorphous. The Mark-Houwink constants for poly (o-vinylbenzophenone) in tetrahydrofuran are K = 4.2 × 10^?2 cm³ g^?1 and a = 0.765. The pre-exponential constant under theta conditions, K_θ, is estimated to be 5.93 × 10^?2 cm³ g^?1. The ratio of unperturbed dimensions of the actual polymer and free rotating analogue chain is 3.93, which is almost double that of polystyrene. The Flory-Huggins interaction parameter for poly $\text{(o-}\text{vinylbenzophenone}\text{)}\text{tetrahydrofuran}$ is 0.48 at room temperature. The $\text{k}{}_{\mathrm{<mtext>p</mtext>}}\text{k}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{<mtext>t</mtext>}}$ ratio at 60°C is $\text{1.1 × 10}{}^{\mathrm{?2}}\text{l}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$. In free radical copolymerizations with styrene at 70°C, r₁ (o-vinylbenzophenone) = 1.216, r₂ = 0.751. This copolymerizations is virtually random.     

Random-coil configurations of alicyclic polyformals

A sample of poly (trans-1,4-cyclohexylene-dimethylene-oxymethylene oxide) (PTCDM) was synthesized by condensation of trans-1,4-cyclohexane dimethanol and paraformaldehyde using p-toluene sulphonic acid as catalyst. A fraction having M_n=6500 and a melting point of 86°C was isolated and purified; its n.m.r. spectrum does not change with temperature in the range 20°–50°C which indicates a rigid distribution of methylene substituents in the cyclohexane ring; its dipole moment, measured in benzene solution at several temperatures between 20° and 60°C, yielded values of $\text{D}{}_{\mathrm{n}}\text{=}\text{[μ}{}^2\text{]}\text{nm}{}^2\text{=0.17–0.21}$ and a temperature coefficient dln $\text{{gm}{}^2\text{}}\text{d}\text{T}\text{= 5.5 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$, similar to those reported in the literature for acyclic polyformals. Agreement between experimental and calculated (using rotational isomeric states theory) values is satisfactory.     

The unperturbed molecular dimensions of poly(ethylene oxide) in aqueous solutions from intrinsic viscosity measurements and the evaluation of the theta temperature

Intrinsic viscosity measurements were carried out on five well characterized fractions of poly(ethylene oxide) in aqueous solutions at 24.9°, 34.9°, and 45.5°C. The Stockmayer-Fixman extrapolation was applied to the data: it yields the unperturbed dimensions K₀ of the chain. The unperturbed root-mean-square end-to-end distance $\text{〈}\text{R}\text{?}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_0$ calculated for the polymer fractions in water indicate that the polymer molecules are expanded in this solvent as the temperature is raised. The temperature coefficient of unperturbed dimension, $\text{d In}\text{〈}\text{R}\text{?}{}^2\text{〉}{}_0\text{d}\text{t}\text{= 0.024}\text{K}{}^{\mathrm{?1}}$, calculated for poly(ethylene oxide) in water using the present data is about 100 times higher than the literature values of 0.23 (±0.02) × 10^?3 K^?1 and 0.2 (±0.2) × 10^?3 K^?1, respectively, obtained from force-temperature (‘thermoelastic’) measurements on elongated networks of the polymer in the amorphouse state and form viscosity measurements on this polymer in benzene. A value of θ=108.3°C was obtained from the temperature dependence of the interaction parameter B in the Stockmayer-Fixman equation.     

Carbon formation from methane in combustion products

The rates of deposition of carbon on alumina surfaces and on soot particles, have been measured in a pilot scale tubular reactor in which cold methane was mixed with combustion products at 1920°K. A hard grey metallic film of carbon, quite free of soot, was deposited on alumina surfaces for initial methane concentrations between 12 and 24 per cent. An induction period of slow growth rate, before a film covered the surface completely, was followed by a constant growth rate. Measured growth rates were from 0·06 × 10^?6 to 1·43 × 10^?6 g/cm² sec of carbon on alumina at 1270°K to 1450°K, and from 0·1 × 10^?4 to 1·14 × 10^?4 g/cm² sec on soot particles at 1370°K to 1700°K. Methane decomposition rates were much higher than predicted by the unimolecular mechanism indicating a predominance of radical reactions. Carbon deposition rates were related to the mole fraction, χ, of hydrocarbons in the gas which bear more than three carbon atoms per molecule, by, $\text{m}\text{?}{}_{\mathrm{f}}\text{= 1·0 × 10}{}^2\text{n.χ}$. exp (?42,300/RT_f), g/cm²sec for carbon film, $\text{m}\text{?}{}_{\mathrm{s}}\text{= 4·6 × 10}{}^3\text{nχ}$ exp (? 46,100/RT_g), g/cm² sec for soot. A precoat of soot increased the growth rate of film carbon by 1·8 to 7·8 times yielding a hard adherent dull brown film     

Properties of extremely high molecular weight polystyrene in solution

Extremely high molecular weight polystyrenes with a $\text{M}\text{?}{}_{\mathrm{w}}$ in the range 10.8 × 10⁶ to 2.2 × 10⁷ were prepared by emulsion polymerization initiated with a heterogeneous initiator at 30°C, which has a ‘living character’. Samples of polystyrene were characterized by light scattering and viscometry in toluene and benzene at 25°C, and in θ-solvent cyclohexane at 34.8°C. Also determined were the relationships of mean-square radius of gyration 〈s²〉 (m²) and the second virial coefficient A₂ (m³ mol kg^?2) on the molecular weight, which for toluene and benzene are described in equations: Toluene (25°C) $\text{〈s}{}^2\text{〉=1.59 × 10}{}^{\mathrm{?23}}\text{M}\text{?}{}_{\mathrm{w}}{}^{1.23}$; $\text{A}{}_2\text{=4.79 × 10}{}^{\mathrm{?3}}\text{M}\text{?}{}_{\mathrm{w}}{}^{\mathrm{?0.63}}$; Benzene (25°C) $\text{〈s}{}^2\text{〉=1.23 × 10}{}^{\mathrm{?22}}\text{M}\text{?}{}_{\mathrm{w}}{}^{1.20}$; $\text{A}{}_2\text{=2.59 × 10}{}^{\mathrm{?3}}\text{M}\text{?}{}_{\mathrm{w}}{}^{\mathrm{?0.59}}$. The parameters in the Mark-Houwink-Sakurada equation were established, for extremely high molecular weight polystyrene in toluene and in benzene, at 25°C into the form giving for $\text{[η] (}\text{m}{}^3\text{kg}{}^{\mathrm{?1}}\text{): [η] = 8.52 × 10}{}^{\mathrm{?5}}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.61}$; $\text{[η] = 1.47 × 10}{}^{\mathrm{?4}}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.56}$. The mentioned relations, as well as the obtained values of Flory parameter ?₀ and of ratio $\text{[η]}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.5}$ were compared with solution properties of high molecular weight polystyrene with narrow molecular weight distribution prepared by anionic polymerization by Fukuda et al.     

Viscometric behaviour of polystyrene in tetralin/cyclohexane mixtures

For solutions of polystyrene (M=10⁵–10⁶ g mol^?1), intrinsic viscosities [η] have been measured at 34.5°C, which is the θ temperature for the polymer in cyclohexane. The solvents comprised cyclohexane in admixture with a thermodynamically good solvent, 1,2,3,4-tetrahydronaphthalene (tetralin, TET) over the whole range of solvent composition. From an assessment of several extrapolation procedures, a value of 85 × 10^?3$\text{(±1 × 10}{}^{\mathrm{?3}}\text{)}\text{cm}{}^3\text{g}{}^{\mathrm{<mtext>?3</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was obtained for K_θ (in the relationship $\text{[η] = K}{}_{\mathrm{\theta }}\text{M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{α}{}^3$, where α is the expansion factor), thus yielding $\text{0.681}\text{A}\text{?}\text{g}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, 2.25 and 10.2 for the unperturbed dimensions, steric factor σ and characteristic ratio C_∞ respectively. The value of K_θ was independent of solvent composition despite the finite excess free energy of mixing for the solvent components alone, which has been asserted elsewhere to affect K_θ. The present results, in conjunction with previous ones relating to 98.4°C, indicate a value of ?0.89 × 10^?3 deg^?1 for the temperature coefficient of the unperturbed dimensions.     

Low frequency excitations in amorphous polycarbonate studied by Raman spectroscopy

Low frequency excitations in amorphous polycarbonate-bisphenol A have been studied by Iaser Raman spectroscopy in the frequency region $\text{5}\text{cm}{}^{\mathrm{?1}}\text{< Δ}\text{v}\text{?}\text{< 200}\text{cm}{}^{\mathrm{?1}}$. Depolarized spectra were recorded at temperatures between ambient and 85 K, the reduced intensity spectra show no temperature dependence. Two bands are resolved in the reduced intensity spectrum: a strong band around 96 cm^?1 and a weak band around 45 cm^?1; these are attributed to the effects of longitudinal and transverse phonon waves originating in backbone motion. The low frequency Raman intensities provide information on the density of state g(ω) from which the specific heat, C_v, of polycarbonate has been calculated. This is found to vary with temperature in a manner similar to the calorimetrically measured C_v in the low temperature range ～1 K < T < 4 K.     

Unperturbed dimensions of poly(phenyl acrylate)

Thirteen fractions of poly(phenyl acrylate) have been prepared with weight-average molecular weight ranging from 0.158 × 10⁶ to 2.57 × 10⁶ g mol^?1. The temperature coefficient of the unperturbed dimensions and the glass transition temperature were found to be ?1.8 × 10^?3 deg^?1 and 55.6°C respectively. Good accord was obtained among different methods for establishing θ-conditions of 11.5°C in ethyl lactate. From viscometry, osmometry and light scattering under θ-conditions, as well as in a good solvent, the unperturbed dimensions were determined via several procedures yielding a value of $\text{[〈r}{}^2\text{〉}{}_{\mathrm{0w}}\text{M}\text{?}{}_{\mathrm{w}}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 6.0 (±0.2) × 10}{}^{\mathrm{?9}}\text{cm g}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. This corresponds to a steric factor υ = 2.37 (±0.08) and a characteristic ratio C_∞ = 11.3 (±0.8). The polymer chain is thus more rigid than poly(methyl acrylate), but less rigid than poly(phenyl methacrylate). With respect to its T_g and flexibility, poly(phenyl acrylate) bears a strong similarity to poly(benzyl methacrylate).     

Low-angle laser light scattering from polystyrene solutions: intensity measurements and photon correlation spectroscopy

Light scattering measurements have been made on polystyrenes with a range of molecular weights in toluene and for one polystyrene with a range of molecular weights in toluene and for one polystyrene in a range of solvents including a theta solvent. Intensity data were used to calculate second virial coefficients and molecular weights, whilst photon correlation spectroscopy was used to calculate diffusion coefficients. All measurements were made at 30°C and at a scattering angle of ca.4°. The data were used to examine current theories of polymer diffusion and the relation between hydrodynamic radius (R_H) and radius of gyrations ($\text{〈s}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$). The results support accepted theories of polymer diffusion, but suggest that the relation between R_H and $\text{〈s}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ requires further analysis.     

Ionic conductivities of poly(methoxy polyethylene glycol monomethacrylate) complexes with LiSO3CH3

Ionic conductivity values for LiSO₃CF₃ complexes with two amorphous poly(methoxy polyethylene glycol monomethacrylates) (PEM) were determined and values as high as $\text{～6 × 10}{}^{\mathrm{?4}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 373 K and $\text{～2 × 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 293 K were achieved. These values are compared with those obtained for a poly(ethylene oxide) (PEO)-LiSO₃CF₃ complex of similar salt concentration with an ether oxygen to Li⁺ ion ratio of 18. The conductivity results for the complexes are similar at temperatures >343 K but at 293 K the values for the conductivities of the PEM-LiSO₃CF₃ complexes are approximately two orders of magnitude higher than those for the PEO-LiSO₃CF₃ complex. This difference is believed to be due at least in part to the presence of a large amount of crystalline material in the PEO-LiSO₃CF₃ complex below 323 K.     

Hydrogen mass transfer in liquid hydrocarbons at elevated temperatures and pressures

The mass transfer rate of hydrogen in tetralin and hydrogenated SRC II liquid was studied in a stirred vessel at 606–684 K and 7.0–13.5 MPa. Experiments were carried out using a newly developed in-situ hydrogen probe made of semi-permeable nickel membrane. The effects of stirrer speed, liquid height to vessel diameter ratio, temperature and pressure on mass transfer rate coefficients were investigated. The experimentally determined $\text{K}{}_{\mathrm{<mtext>l</mtext>}}\text{a}$ values were correlated in terms of power input per unit volume of liquid and liquid height to vessel diameter ratio as follows: $\text{k}{}_{\mathrm{<mtext>L</mtext>}}\text{a = 3.43 × 10}{}^{\mathrm{?4}}\text{(}\text{P}\text{V}\text{)}{}^{0.8}\text{(}\text{H}\text{D}{}_{\mathrm{<mtext>T</mtext>}}\text{)}{}^{\mathrm{?1.9}}$ Furthermore, the liquid-phase mass transfer coefficient, $\text{k}{}_{\mathrm{<mtext>l</mtext>}}$, was found to be of the order of 10^?5 m s^?1 for low agitator speeds.     

Ionic conductivities for poly(ethylene oxide) complexes with lithium salts of monobasic and dibasic acids and blends of poly(ethylene oxide) with lithium salts of anionic polymers

Lithium salts of two polyanionic addition polymers containing alkyl sulphonic acid and perfluoroalkyl carboxylic acid side groups were prepared. Blends of these polymers were formed with poly(ethylene oxide) (PEO). The blend containing alkyl sulphonate units showed some phase separation but this was not observed for the blend containing perfluoroalkyl carboxylate groups. In the latter case a comparatively high conductivity of $\text{～10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}$ cm^?1 at 374 K was obtained. The anionic units in these blends are expected to be virtually immobile. Complexes formed from PEO and the Li-salt of hexafluoroglutaric acid had similar high ionic conductivities and there are grounds for supposing that the anions in these complexes may also be substantially immobilized. In addition, conductivity values were obtained for some PEO complexes containing lithium salts of some monobasic acids and it was found that the complex formed from the Li-salt of the strongest acid gave the highest conductivity ($\text{～4 × 10}{}^{\mathrm{?4}}\text{Ω}{}^{\mathrm{?1}}$ cm^?1 at 373 K for a PEO-LiSO₃CF₃ complex).     

Phosphonitrilic chloride: 34. Electrical conductivity of polybisaminophosphazenes

The electrical conductivity of polybisaminophosphazenes investigated over a range of temperatures was found to obey the general relation for semi-conductors. The resistivity decreased or increased when a side group having a high inductive effect or bulky group was linked in the polymers. The electrical conductivity of polybisaminophosphazenes containing primary amine, secondary amine and aromatic amine ranged from 1.3 × 10¹⁰ to $\text{2.8 × 10}{}^{10}\text{Ω-}\text{cm}$, 9.3 × 10¹⁰ to $\text{8.5 × 10}{}^{11}\text{Ω-}\text{cm}$ and above $\text{9.1 × 10}{}^{14}\text{Ω-}\text{cm}$, respectively.     

Low frequency excitation in amorphous acrylic polymers

Low frequency Raman depolarized spectra from poly(methyl methacrylate) have been determined at temperatures between 293 K and 85 K in the frequency region $\text{5}\text{cm}{}^{\mathrm{?1}}\text{<}\text{v}\text{?}\text{<2000}\text{cm}{}^{\mathrm{?1}}$. All the reduced intensity spectra resolve into two bands: a broad and intense band at 91 cm^?1 and a narrower and weaker band at 22 cm^?1. The Raman intensities do not depend on temperature which implies first order Raman scattering. Room temperature low frequency Raman spectra were also recorded from poly(ethyl methacrylate) and poly(-n-butyl methacrylate). In the two PMMA substitutes the high frequency band is shifted to lower values as the side group mass is increased and show a Debye-like character. The lower frequency band cannot be resolved in the spectrum of PEMA and PnBMA. The two bands at 91 cm^?1 and 22 cm^?1 are attributed to side group and backbone motions respectively. By studying PMMA samples of different tacticity no dependence of the band frequency on chain configuration has been detected. The density of states g(Ω) obtained through the low frequency Raman spectrum has been used to calculate the specific heat C_v. The values of C_v obtained are lower than those measured calorimetrically but varied with temperature in a similar manner in the region 0.8<T<4K.     

Small-angle neutron scattering studies of molten and crystalline polyethylene

Small-angle neutron scattering studies have been made of molten and crystalline polyethylene using samples containing small amounts of deuterated polyethylene (PED) in a protonated polyethylene (PEH) matrix. Careful studies were made of PED aggregation effects, and by a combination of solution blending techniques and rapid quenching from the melt, it was possible to prepare samples with a statistical distribution of PED molecules in the PEH matrix. Measurements of radius of gyration $\text{(S}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{w}}$ at low κ [$\text{κ = (}\text{4π}\text{λ}$) sin $\text{? ≤ 2 × 10}{}^{\mathrm{?2}}\text{A}\text{?}{}^{\mathrm{?1}}$] in the melt and in the solid state gave very similar values which may be summarized as $\text{〈S}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{w}}\text{= (0.46 ± 0.05)M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{w}}$ for both phases. This correspondence of values indicates that on a rapid quench, diffusion is sufficiently slow that the molecule crystallizes with a similar spatial distribution of mass elements to that possessed in the melt. Measurements of scattering data over a wide κ range ($\text{6 × 10}{}^{\mathrm{?3}}\text{≤ κ ≤ 0.12}\text{A}\text{?}{}^{\mathrm{?1}}$) have also been made from samples showing no aggregation effects. Calculations indicate that it is difficult to fit this data in terms of models which postulate adjacent chain re-entry in one crystallographic plane for this type of sample.     

Solution properties of poly(propylene sulphide)

Poly(propylene sulphide) (PPS) initiated by cadmium bis(phenyl allyl thiolate) was fractionated from benzene-methanol, and the fractions were examined by viscosity, osmotic pressure and light scattering determinations. Gel permeation chromatography with Styragel columns was found unsatisfactory in tetrahydrofuran (THF) and toluene at room temperature. Polymer stored in the dark at room temperature underwent a very slow degradation which broadened the distribution in the fractions. The following quantitative relationships were found at 25°C:

Extrapolations to derive the unperturbed coil dimensions indicate a possible, but doubtful, solvent effect. The value derived from the θ-mixture gives $\text{A = 696 × 10}{}^{\mathrm{?11}}\text{cm mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{g}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$ and a steric factor σ = 1.49, consistent with a high ‘chain flexibility’ expected from the relatively long C-S-C linkages.     

Macromolecular properties of heparin in dilute solution: 2. Dimensional parameters as a function of pH,ionic strength and desulphation

A bovine heparin fraction was examined by sedimentation analysis and intrinsic viscosity measurements as a function of ionic strength in the range of 0·1 to 1·0 M, and at pH 2·5 and 6·0. The following experimental parameters were obtained: M, S⁰_20,W, D⁰_20,W, $\text{V}\text{?}$, and [η]. Other physical parameters were calculated based on a random coil model (supported by the theory of Mandelkern and Flory) e.g., $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. Similar studies were made on a heparin sample as a function of desulphation as resulting from graded mild hydrolysis. Since desulphation is accompanied by decreasing anticoagulant activity of heparin, the latter was correlated with various calculated and measured physical parameters. Significantly $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ decreases with decreased desulphation and therefore decreased biological activity.     

Poly(ethyl acrylate) in dilute solution

Poly(ethyl acrylate) (PEA), solution polymerized in methyl ethyl ketone by free radical initiation, was fractionated and the fractions were characterized by light scattering, viscometry and osmometry. Fractions obtained were in the molecular weight range of 0·3 × 10⁶ to 1·6 × 10⁶ with a polydispersity of 1.40. The following Mark-Houwink relations were established:

$\text{[η]}{}^{\mathrm{<mtext>35°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>acetone</mtext>}}\text{=4·15×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?61}}{}_{\mathrm{W}}$

$\text{[η]}{}^{\mathrm{<mtext>35°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>MEK</mtext>}}\text{=2·03×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?66}}{}_{\mathrm{W}}$

$\text{[η]}{}^{\mathrm{<mtext>39.5°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>n-propanal</mtext>}}\text{=7·89×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?50}}{}_{\mathrm{W}}$

It was found that n-propanol at 39.5°C was a theta solvent for poly(ethyl acrylate) and that acetone was a poor solvent compared to methyl ethyl ketone. A relation between the molecular dimension and the molecular weight was established. It was observed that the chain dimensions of poly(ethyl acrylate) and poly(butyl acrylate) were considerably larger than poly(ethyl methacrylate) and poly(butyl methacrylate) respectively. The validity of various extrapolation procedures that have been proposed for calculating the unperturbed dimensions have been examined. The steric factor for PEA was 2·16 compared to 2·10 for poly(ethyl methacrylate). Root mean square end-to-end distances were calculated from the Debye-Bueche and Kirkwood-Riseman methods and compared with the experimental values.     

Laser flash photolysis studies on homo-and copolymers of phenylisopropenyl ketone and of pivalophenone in solution

Benzene solutions of poly(phenylisopropenyl ketone) (PPIK), of copolymers of PIK and styrene and of phenyl-t-butyl ketone (pivalophenone) were irradiated with light flashes (duration 25 nsec) at wavelength 347 nm. The spectra observed at the end of the flash were attributed to the triplet state (T-T-spectra). A fraction of the triplets in the polymers was deactivated by T-T annihilation, as evidenced by lifetimes decreasing with increasing absorbed dose rate. Upon extrapolation to zero intensity the following triplet decay rate constants K_T were obtained:

$\text{(1.0 ± 0.1) 10}{}^7\text{sec}{}^{\mathrm{?}}\text{(}\text{PPIK}\text{),}$

$\text{(8 ± 1) 10}{}^6\text{sec}{}^{\mathrm{?1}}\text{(}\text{CPStPlK12}\text{), (6 ± 1) 10}{}^6\text{sec}{}^{\mathrm{?1}}\text{(}\text{CPStPlK3.7}\text{)}$

$\text{(3 ± 1) 10}{}^6\text{sec}{}^{\mathrm{?1}}\text{(}\text{CPStPlK1}\text{)}$

$\text{(2.5 ± 0.2) 10}{}^6\text{sec}{}^{\mathrm{?1}}\text{(}\text{pivalophenone}\text{)}$

.In PPIK and pivalophenone the dominant chemical route of triplet deactivation is α-cleavage. The relatively high k_T value found with PPIK is presumably due to next neighbour interaction. In copolymers with a high content of isolated PIK units type I processes (α-cleavage) become less probable due to weak next neighbour influence. Thus type II processes dominate in copolymers although being slower than type I processes in homo PPIK. The rate constant of the reaction of PIK triplets in homo PPIK with 2-propanol in benzene solution is (2.0 ± 0.2)10⁶ l/mol sec, whereas pivalophenone triplets react almost 10 times slower with 2-propanol. The difference is assumed to be due to a rather strong interaction of 2-propanol with ground state as well as with excited pivalophenone.