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Small-angle X-ray scattering (SAXS) has been applied in obtaining the solution parameters (molecular mass M, radius of gyration Rg, radius of gyration of cross-section Rq, mass per unit length Mu, and persistence length a ∗ ) of a poly(acrylic acid) (PAA) sample in dioxane at 25°C. The M and Rg values measured from SAXS were 552 000 Da (daltons) and 292 A, respectively. These values are in reasonable agreement with those obtained from solution viscometry measurements on the same sample of PAA in dioxane at 30°C ( M = 567 000 Da and R g = 227 A ). The Rq and a ∗ values obtained from SAXS were 6.1 A and 14.4 A, respectively. The Mu value measured from SAXS is 27.9 Da A−1, in excellent agreement with the model (theoretical) value of 28.6 Da A−1 calculated from the structure and molecular mass of the monomer unit. The length L (= M/Mu = 19 790 A) obtained from SAXS thus corresponds to the contour length of the molecule and not to the ‘hydrodynamic’ length (i.e. the length the chain assumes in the fluid medium).

The kinetics of the acid degradation of Streptococcus salivarius levan was studied by observing changes in the number-average molecular weight, Mn, using end-group analysis. Rate constants for the hydrolysis are presented and a tentative mechanism is forwarded. The data has been analysed according to a statistical model for a polymer with trifunctional branching and it is shown that the hydrolysis of levan proceeds through a mechanism quite different to that reported for the polysaccharide dextran.

Bovine heparin was fractionated according to molecular weight by fractional precipitation utilizing a method described previously. The solution data from sedimentation analysis, intrinsic viscosities and partial specific volumes at pH 2·5 and in 0·5 M NaCl were treated according to the Mandelkern and Flory theory for random coil in calculating the constant β. It was found that the calculated β values for all the fractions were in close agreement with the theoretical value. Based on this observation, the solution data were then treated in light of various hydrodynamic theories for linear polymers to calculate various dimensional and other physical parameters, e.g., ( r 2 ) 1 2 , α (expansion factor), A 2 . In comparing ( r 2 ) 1 2 of a fraction to that calculated from the experimental value of ( s 2 ) 1 2 obtained from low angle X-ray scattering for a comparable molecular weight sample, it was found that heparin in solution with suppressed charges may best be described as approximating the closely related models of Debye and Bueche, Flory and Fox, or Kuhn and Kuhn.

Isotactic poly(1-pentene) was degraded in the presence of pure oxygen at 115°C. The functional groups present in the non-volatile products were identified using infra-red spectroscopy. The volatile products formed were identified by means of a relatively new technique which combines thermal and mass chromatography. In this study, fourteen volatile products were detected and identified and their relative abundance estimated. The results obtained could readily be reproduced. Various oxidation mechanisms for these products are postulated.

The viscosity of heparin was examined in pure glycerol, formamide and in mixtures of the two solvents. This study confirms that the equation η sp c = [η] ∞ [1 + k (c) 1 2 ] , where [η]∞ is the shielded intrinsic viscosity, adequately describes the concentration dependence of the reduced viscosity of the polyelectrolyte, heparin. The [η]∞ linearly increases with the dielectric constant of the solvent.

The kinetics of the thermal oxidation of isotactic poly(1-pentene) was studied in the bulk phase. The experimental data were obtained from the quantitative estimation of carbonyl groups formed in the non-volatile oxidation products using infra-red spectroscopy. Reaction temperature varied from 100° to 115° and oxygen concentrations from 10% to 100% by volume. A general kinetic scheme and mathematical expressions previously reported for the thermal autoxidation of polyolefins satisfactorily explained the experimental results. Activation energies of this polymer for various steps in the kinetic scheme were compared with polypropylene and poly(1-butene).

Small-angle X-ray scattering, SAXS, measurements were obtained from 12-arm near-monodisperse star polystyrenes in methyl ethyl ketone at 25°C. Calculations from the SAXS data yielded information on the molecular weight, Ms, the radius of gyration, Rg, mass per unit length, mu, radius of gyration of the crosssection, Rq, and persistence length, a∗. Values of Ms and Rg from SAXS were in good agreement with values obtained from light scattering. A branching parameter in terms of a∗, s = a∗1a*b where subscripts l and b refer to linear and branch, respectively, is introduced and related in terms of functionability, f, or g, where g = (Rg)b(Rg)l.

The kinetics of the thermal oxidation of isotactic and atactic poly(4-methyl-1-pentene) were studied in the bulk phase using infra-red (i.r.) spectroscopy. The rates of formation of the non-volatile products were assessed from the i.r. bands of the carbonyl groups at different temperatures and various oxygen concentrations. Reaction temperature varied from 120° to 185°C and oxygen concentrations from 10 to 100%, by volume. A general kinetic scheme and mathematical expressions, previously reported for the thermal oxidation of polyolefins, satisfactorily explained the experimental results. Single activation energies for the major oxidation stages in the scheme, were estimated from various Arrhenius plots.

Comb-branched polystyrenes having both fixed backbone length and number of branches but variable branch lengths were prepared anionically. Small angle X-ray scattering of the model polystyrenes from methyl ethyl ketone (MEK) solutions at 25°C was examined and it is shown that the mass per unit length and cross-sectional radius of gyration increase with increasing branch length. A maximum appears in the Kratky plot for the branched polymers. While the linear polymer displays an essentially Gaussian segment distribution in solution, the branched polymers deviate considerably from the behaviour of the linear polymer under the same conditions.

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 , S 0 20,W , D 0 20,W , V , and [η]. Other physical parameters were calculated based on a random coil model (supported by the theory of Mandelkern and Flory) e.g., ( r 2 ) 1 2 , ( s 2 ) 1 2 . 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 ( r 2 ) 1 2 decreases with decreased desulphation and therefore decreased biological activity.

The kinetics of the thermal oxidation of isotactic poly(4-methyl-1-pentane) were studied in the bulk phase using thermogravimetric analysis (t.g.a.) at temperatures from 155° to 185°C and oxygen concentration from 75 to 100% by volume. The kinetics derived from formation of volatile products using t.g.a. correspond to those from non-volatile carbonyl products obtained from infra-red spectrometry.