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Positrons which penetrate and become trapped in polymeric solids form states which display complex annihilation time spectra. The average lifetimes and intensities of the posiltron states can be obtained from the exponentially decaying components of the time spectra. Usually three components can be resolved for solid polymers; with long, Intermediate and short average lifetimes. Experimental results of lifetimes and intensities for positrons annihilating in trans 1–4 polybutadiene, polyethylene, polyethyleneterephthalate are used to conclude that the intensity can be associated with regions of short range order and the intermediate lifetime and intensity with regions of long range order. It is also concluded that for both regions of long range and short range order there is a tightening of the microstructure in the polymer as the amount of long range order increases and/or molecular weight decreases.

Mutations of esterase 3 confer two forms of organophosphate resistance on contemporary Australasian Lucilia cuprina . One form, called diazinon resistance, is slightly more effective against commonly used insecticides and is now more prevalent than the other form, called malathion resistance. We report here that the single amino acid replacement associated with diazinon resistance and two replacements associated with malathion resistance also occur in esterase 3 in the sibling species Lucilia sericata , suggesting convergent evolution around a finite set of resistance options. We also find parallels between the species in the geographic distributions of the polymorphisms: In both cases, the diazinon-resistance change is absent or rare outside Australasia where insecticide pressure is lower, whereas the changes associated with malathion resistance are widespread. Furthermore, PCR analysis of pinned specimens of Australasian L. cuprina collected before the release of organophosphate insecticides reveals no cases of the diazinon-resistance change but several cases of those associated with malathion resistance. Thus, the early outbreak of resistance in this species can be explained by the preexistence of mutant alleles encoding malathion resistance. The pinned specimen analysis also shows much higher genetic diversity at the locus before organophosphate use, suggesting that the subsequent sweep of diazinon resistance in Australasia has compromised the scope for the locus to respond further to the ongoing challenge of the insecticides.

Amorphous poly(propylene oxide), PPO (molecular weights, 425 and ∼106), complexed with NaClO4 salt has ionic conductivities as high as 10−5 S/cm at room temperature. In an attempt to directly study the dynamics of the Na+ ions, (I=3/2) nuclear magnetic resonance (NMR) spin-lattice relaxation times, T1, and spin–spin relaxation times, T2, at a resonance frequency of 77.0 MHz have been measured over the temperature range from 150 to 390 K. A range of salt compositions [(PPO)nNaClO4; n=8–30] have been investigated. In addition, the glass transition temperature for each sample is reported. The recovery of equilibrium magnetization following a π/2 pulse is biexponential as expected for a spin I=3/2 system in the viscous liquid region. Below Tg a better fit to the magnetization recovery curve can be obtained if Kohlrausch–Williams–Watts (KWW) functions are used in place of the exponential functions. At low temperature the molecular motion has slowed to the point where a common spin temperature is not achieved b...

Stable to atmospheric moisture, adhesive and transparent polymer electrolytes have been prepared by blending poly (methyl methacrylate) (PMMA) with poly(propylene glycol)-425/LiCF 3 SO 3 complexes. The blending of the polymers has been achieved by free radical polymerization of MMAin the polyether/salt matrix. A series of polymer blend complexes varying in PMMA content (up to 20% by weight) and oxygen/metal ratios (25, 16, and 8) have been synthesized and their properties studied

Poly (ethylene oxide) and poly (propylene oxide) modified poly (dimethyl siloxane) (PDMS) have been complexed with LiCF3SO3, NaCF3SO3 and KCF3SO3. In order to study ion association in these systems, the nondegenerate symmetric stretch (A1, SO3) Raman modes have been studied as a function of temperature at several different salt concentrations. Ionic conductivity has also been measured. For the poly (ethylene oxide) modified PDMS (PEO-PDMS), ether oxygen to metal ratios ranged from 12500:1 to 9:1. Changing the cation from Li+ to Na+ to K+ increases the conductivity of the complex. Plots of the molar conductivity versus salt concentration show the characteristic shape and the region of increase in the molar conductivity is influenced most by the fraction of “free” ions which increases with increasing salt concentration. Charged triplets and contact ion-pairs are also present at the higher salt concentrations; the number of triplets increases with concentration and temperature. Non-VTF behaviour is observed. For the poly (propylene oxide) modified PDMS (PPO-PDMS) (with excess PPO), phase separation is observed when these triflate salts are complexed in. These solutions above and below the boundary layer have been studied by Raman spectroscopy revealing that the upper region is siloxane rich. The formation of the boundary layer is attributed to an increasing difference in surface tension between the PPO/salt/PPO-PDMS complexes and the separate PPO, PPO-PDMS components. The boundary layer moves up with increase in salt concentration. There is evidence of “free” ions, contact-ion pairs, triplets and aggregates. Values of conductivity of 2.2×10−6 and 1.6×10−5 S/cm are quoted for 293 K and 8 mol% LiCF3SO3 in respectively PPO-PDMS/PPO and PEO-PDMS/PEO. Both are better conductors than the corresponding 8 mol% PPG4000/LiCF3O3 complex. LiCF3O3 complex.

Phase separation is observed in poly(propylene oxide) modified poly(dimethylsiloxane) (PPO-PDMS) with excess poly(propylene oxide) (PPO) when salts of MCF 3 SO 3 (M = Li, Na) are added. The same behaviour is inferred for KCF 3 SO 3 . The solutions above and below the boundary layer have been studied by Raman spectroscopy and in particular by examining the non-degenerate, symmetric stretch ( A 1 , SO 3 ) Raman mode of the CF 3 SO − 3 anion. The upper part is siloxane rich; salt is present on both sides of the boundary layer with a much lower concentration in the upper part. The formation of the boundary layer is attributed to an increasing difference in surface tension between the PPO/salt/PPO-PDMS complexes and the separate PPO, PPO-PDMS components. The boundary layer moves up with increase in concentration. The number of ‘free’ ions decreases and ion association increases with increase in temperature. There is evidence of contact ion pairs, triplets and aggregates. Values of conductivity are quoted for 293 K.

The electric modulus representation is used to display conductivity and dielectric relaxation occurring in poly(propylene glycol)‐4000 (PPG) complexed with LiCF3SO3, as the ether oxygen to lithium (O:Li) ratio is varied from 300:1 to 12:1. The frequency range covered is 10 to 107 Hz. Results are obtained for temperatures above the glass transition temperature appropriate for each PPG–LiCF3SO3 complex. For O:M=300:1, the conductivity peak and the α and α’ relaxation are clearly resolved. As the concentration is increased, there is a coupling between the structural and the conductivity relaxations; the various peaks begin to overlap. The coupling is greatest for an O:Li ratio in the range 30:1 to 12:1, where the highest conductivity is measured. Below room temperature, the 30:1 complex has the highest conductivity, above room temperature the 12:1 complex has the highest. At any particular temperature there is a concentration above which the conductivity drops. This drop is due to reduced ion mobility result...

The empirical response function introduced by Cole and Davidson for the analysis of dielectric relaxation in the frequency domain has been used in an analogous way to reanalyze ionic conductivity relaxation using the electric modulus representation. The fitting of data for ionic relaxation in AgPO3, 0.1AgI‐0.9AgPO3, and 0.4Ca(NO3)2‐0.6KNO3 originally fit using a Kohlrausch–Williams–Watts response function has been considerably improved.

We have used Brillouin light scattering (BLS) to measure the glass transition temperature of thin, freely-standing poly(styrene) (PS) films. The freely-standing films were prepared by spincoating solutions of PS in toluene onto glass substrates, annealing the supported films in vacuum, and then using a water surface transfer technique to place the films across a 3 mm diameter orifice. Ellipsometry measurements of similar floated films transferred to Si(001) wafers allow the determination of the film thicknesses. Atomic force microscopy measurements revealed that the films have an rms roughness of less than 10 A˚. With the freely-standing films placed in an optical furnace, we performed BLS measurements of the films using a high-contrast, multipassed, tandem Fabry-Perot interferometer. We obtained a reliable, reproducible measure of the glass transition temperature, Tg, from the large changes in the frequencies of the thermally-excited, viscoelastic, film-guided waves within the PS films as the films were heated above Tg. BLS results for bulk PS and a 1800 A˚ thick, freely-standing PS film are presented. We find the same glass transition temperature for the 1800 A˚ thick film as the bulk PS sample. This Tg value is the same as that obtained using differential scanning calorimetry (DSC).

We present a study of the effect of elevated temperatures on the high frequency viscoelastic waves guided by thin films of poly(styrene) [PS] and poly(methyl methacrylate) [PMMA]. The films, which are spincoated onto Si(OOl) wafers, have thicknesses h ˜ 1000 Å. The frequencies and linewidths of the film-guided waves were measured using Brillouin light scattering (BLS). In both PS and PMMA, we observed guided waves for temperatures above the glass transition temperature Tg of the polymers, however, the damping of the waves for temperatures above Tg was significantly higher for PS. We observed no significant (< 1 %) difference between room temperature guided-wave frequencies for films annealed at temperatures below and above Tg for PS, and a slight (4 %) increase in the wave frequency for PMMA following annealing at a temperature above Tg. The heating effects due to the focussing of the laser beam on the film surface are quite small (˜ 16°C/100 mW laser power).

Brillouin light scattering (BLS) has been used to study a series of three thin films of poly(styrene) spin coated onto Si(001) wafers. Poly(styrene) molecular weights Mw of 30 000 and 600 000 were used, and the film thicknesses h were in the range 1730 A

A growth-promoting agent for the human neuroblastoma cell line SK-N-SH(EP) (SH-EP) has been detected in human cerebrospinal fluid (CSF) derived from schizophrenic patients. Following treatment with the CSF, a number of properties of the SH-EP cells changed permanently. These included an accelerated rate of growth, an increased cell density at confluence, a change of cell shape, and an increased ability to form colonies in soft agar. All of these changes are consistent with further cellular transformation of the SH-EP cells. Once the cells' properties had changed following CSF treatment, the growth-promoting activity was found to be present in freeze-thawed cell extracts and in the culture medium, and could be passed to untreated SH-EP cells. The activity could be detected in culture media diluted as high as 108. It was inactivated by proteinases, chloroform, or heat but passed through a 0.22-μm filter. The growth-promoting activity can be banded on a Percoll gradient, suggesting that it is particulate rather than a soluble growth factor. © 1993 Wiley-Liss, Inc.

An optically homogeneous sample of highly syndiotactic poly(n-butyl methacrylate) (PBMA) has been prepared. The glass transition temperature was observed to be Tg=55C. Measurements of the scattered intensity of the sample followed the expected behavior for a pure liquid above Tg. The intensity rose as the sample was cooled further towards the glass transition temperature for atactic PBMA. These results illuminate the importance of regions of different stereoisomers in methacrylate polymers. Measurements of the Rayleigh- Brillouin spectrum were carried out from -15 to 130 C. The ratio of the the central peak intensity to the Brillouin intensities at temperatures above Tg was consistent with a viscoelastic liquid and had a magnitude near 3. The Brillouin linewidth remained large near Tg. and decreased continuosly with no apparent change in slope in the glass transition region. The presence and importance of rapid motions in polymers near the glass transistion is demonstrated by these results. Slowly relaxing density fluctuations near Tg. were measured by photon correlation spectroscopy. Relaxation functions were obtained from 10−6 to 10 s. Average relaxation times were obtained from the integral of the relaxation function and were found to follow the relation =Aexp(B/(T−T0)), where for our sample B=2940K and T0=273K. The observed relaxation function decayed over a wider time range as the sample was cooled. Quantitative analysis of this effect using the Williams-Watts empirical function yielded a decrease in β from 0.35 at 90 C to 0.18 at 65 C. The relaxation functions were also analyzed to give a distribution of relaxation rates. The observed distributions were bimodal at 70 and 80 C. The two features behaved in a manner consistent with the primary and secondary relaxations observed for methacrylate polymers by other techniques.

The thermal polymerization of clean styrene has been studied through Rayleigh-Brillouin light scattering. The frequency shifts, Rayleigh to Brillouin intensity ratios, Rayleigh depolarization ratios, and depolarized intensities were measured as the polymerization proceeded to completion at 90°C. The depolarized intensities decreased and the frequency shifts increased smoothly from the monomer to the polymer values. The Vv intensities and Rayleigh to Brillouin intensity ratios increase dramatically during the first stages of polymerization then decrease systematically to their final values. There is a large increase in the Rayleigh to Brillouin intensity ratio from the monomer to the final polymer value. The vertical depolarization ratio pv and the horizontal depolarization ratio pV were found to be respectively 0.4 and 1 for the polymer. Our observations are explained in terms of light being scattered from concentration fluctuations in the early stages of polymerization and from spherically symme...

Brillouin frequency shifts from light scattering are used to measure the variation with pressure of the zero‐frequency glass transition temperature T g in atactic polystyrene (PS) at pressures up to 3 kbar. These results are extrapolated to high pressures and compared with theoretical predictions. Experimentally it is found that T g asymptotically approaches a critical value at high pressures. The equilibrium lattice model of DiMarzio, Gibbs, Fleming, and Sanchez which approximates the residual entropy of a polymeric glass correctly predicts the experimentally observed trends. The molecular theory of Bengtzelius, Gotze, and Sjolander is also qualitatively correct at high pressures even though it deals with the glass transition of a classical monatomic fluid. Neither theory is quantitatively in agreement with our results.

The central Lorentzian peak in the depolarized Rayleigh spectrum of CCl4 and GeCl4 is studied as a function of temperature using a high resolution Fabry–Perot interferometer. The results are shown to be consistent with a recent theory by Madden which attributes the depolarized spectrum to scattering by anisotropic pairs of density fluctuations. It is also shown that the ubiquitous presence of long‐lived asymmetric vibrationally excited molecules may give rise to a spectrum whose width is determined by the reorientational relaxation time of the molecules. In the molecules studied here, the two relaxation times are comparable.

The frequencies and intensities of the Raman spectrum of thermally polymerizing styrene were measured in order to confirm (or correct) the mode assignments in the literature and to observe the effect of polymerization on the Raman active modes. The spectra were measured over a period of three weeks while an originally highly purified sample of monostryrene was kept at about 100 °C. The polymer vibrations are identified with their monomer ’’origins’’ which are in turn compared to known benzene (or benzene derivatives) and ethylene (or vinyl group) vibrations.

Photon correlation spectroscopy is employed to study the slowly relaxing density and anisotropy fluctuations in bulk atactic polystyrene as a function of temperature from 100 to 160°C and pressure from 1 to 1330 bar. The light-scattering relaxation function is well described by the empirical function ϕ(t) = exp[−(t/τ)β], where for polystyrene β = 0.34. The average relaxation time is determined at each temperature and pressure according to 〈τ〉 = (τ/β)Γ(1/β) where Γ(x) is the gamma function. The data can be described by the empirical relation 〈τ〉 = 〈τ〉0 exp[(A + BP)/R(T − T0)] where R is the gas constant and T0 is the ideal glass transition temperature. The empirical constant A/R is in good agreement with that determined from the viscosity or the dielectric relaxation data (1934 K). The empirical constant B can be interpreted as the activation volume for the fundamental unit involved in the relaxation and is found to be comparable to one styrene subunit (100 mL/mol). The quantity B appears to be a weak function of temperature. The use of pressure as a tool in the study of light scattering near the glass transition now has been established.

The Raman spectra of styrene and atactic polystyrene have been recorded at 85 and 225 K. As the temperature is lowered, all 42 vibrational modes of the styrene molecule were resolved including those normally of very low intensity in Raman scattering. A general increase in the intensity of all lines and in the number of overtones and combination bands was observed. The frequency of out‐of‐plane vibrational modes was increased due to increased steric hindrance, whereas the frequency of in‐plane modes remained relatively stable. Of particular interest are 11 low frequency modes, most of which are believed to track low frequency benzene‐vinyl torsional oscillations from gaseous styrene and are enhanced by the crystal field. Depolarization ratios were measured for styrene at 300 K and polystyrene at 300 and 85 K. We have confirmed that there is some correlation between very symmetric vibrational modes in styrene and atactic polystyrene and strong polarization (ρV

The technique of depolarized Rayleigh light scattering spectroscopy has been applied to follow the kinetics of the thermal polymerization of styrene. By measuring the spectrum of the depolarized scattered light we are able to separate the intensity of light scattered by the polymer being formed from the intensity of light scattered by the monomer. The spectrum consists of a wide Lorentzian due to the monomer and a central spike with instrumental width due to the polymer. This separation occurs because the polymer relaxation time which is determined by the longest Rouse–Zimm mode or by overall rotation is four orders of magnitude longer than the relaxation time of the monomer which is governed by overall rotation. Using the intensity data, the initial rate of the polymerization reaction is measured and is found to agree with the rate determined in previous experiments using classical techniques. After about one‐third of the reaction is complete, the rate increases by 50%. This increase in rate is interpret...

Rayleigh‐Brillouin light‐scattering studies have been carried out on atactic polystyrene thermally polmerized under vacuum from scrupulously clean styrene monomer. The ratio of the central Rayleigh intensity IR to the total Brillouin intensity 2IB appears to be a function of T−1. Depolarization intensities have also been measured and, in particular, we find that ρH=1 for this polymeric glass. Theoretical predictions for IR/2IB are discussed in light of these results. We conclude that local isotropy due to strain fields frozen into glass is negligible or in low concentration. Annealing studies confirm this result which is in disagreement with our previous results for poly(butyl) methacrylate. In addition, we find that the change in slope of the Brillouin frequency shift ω versus absolute temperature T defines a Tg 10–12 K below that measured by DSC and that ω (glass) increases with decreasing molecular weight, in agreement with previous results. A study of the relaxation of a few degrees below Tg for perio...

The Raman spectrum of thermally polymerizing styrene has been recorded for temperatures of 100 and 70 °C. The intensities of the ν9 (C = C stretch mode) and ν14 (C–H bending mode) in the vinyl group are used as an indicator of the percent conversion from monomer to polymer. These intensities, normalized to that of ν24 (phenyl breathing mode), are compared to the depolarized Rayleigh intensity of polymerizing styrene. It is suggested that there is very little orientational correlation between the polymer and monomer molecules.

Accurate measurements of the depolarized Rayleigh-Brillouin light scattering spectrum have been made on pure styrene as it thermally polymerizes. The ratio of the depolarized scattering per unit volume of the monomer to that of the polymer is observed to be constant as polymerization proceeds; the value of this ratio was determined to be 2.61 ± 0.06.

Polarized Rayleigh scattering is studied near the glass-rubber relaxation in atactic polystyrene using photon correlation spectroscopy. Average relaxation times determined from the data agree well with previous results obtained using depolarized Rayleigh scattering. The light scattering results follow the same trend observed by dielectric and mechanical relaxation studies, but the times for orientational relaxation are longer by approximately two orders of magnitude. Also, an extensive discussion of the experimental techniques necessary to use photon correlation spectroscopy of polymers near the glass-rubber relaxation is presented.

Rayleigh–Brillouin light scattering studies have been peformed on samples of pure atactic polystyrene which has been subjected to a densification cycle. On reheating the densified glass isobarically at low pressure a significant increase is observed in the Rayleigh intensity in temperature regions associated with motion of the phenyl side groups below Tg ( β relaxation) and with rearrangement of the chain backbone above Tg (α relaxation). This enhanced scattering intensity is attributed to nonuniform density distributions created in the sample as the long chain molecules return to configurations appropriate to the nondensified glass and the equilibrium melt. There is only a slight difference in the values of the hypersonic velocity between the densified and nondensified glasses and no difference in the equilibrium melt.

Stress-temperature (constant strain) and length-temperature (constant stress) measurements have been made on Paracril-35 (a butadiene-acrylonitrile copolymer) in the temperature range −80° C to 25° C, which includes the glasslike, transition, and rubberlike states for this material (Tg∼−25°C). Time effects are observed in the transition region, but for temperature gradients used (down to about 1° C in 4 hours) the behavior at low temperatures is unique, indicating the existence of a real transition. This behavior is independent of the strain imposed at room temperature. The shift in transition temperature (in the length-temperature work) with extension is found to give quantitative support to the theory that the transition occurs at a certain minimum volume. In the rubberlike region, behavior is represented by the usual equation of state.

Several ammine complexes of osmium(II) containing one or two π-acceptor ligands have been prepared. They have been characterized by analytical techniques and their infrared and electronic spectra have been recorded and assignments proposed. Comparison with similar ruthenium(II) complexes has been made when possible.

The hypersonic elastic constants and the ratio of the elasto‐optic coefficients for two lead silicate optical‐grade glasses and for a zinc silicate optical‐grade glass have been obtained by observing the Brillouin scattering of 6328‐A laser light over the temperature range 24–107 °C. Brillouin scattering at 90° from both the transverse and longitudinal acoustic modes has been observed. The values of the hypersonic Young's modulus and shear modulus agree with low‐frequency values and show a slight temperature dependence. Poisson's ratio and the ratio of the elasto‐optic coefficients are found to be independent of temperature over the temperature range used. There is no evidence of dispersion from audio to hypersonic frequencies.

A detailed study was made of the relative spectral distribution of sun-sky radiation at several times of day under various sky conditions from June to October 1971. A sufficient number of spectra were recorded to provide a statistically viable sample. Average spectral distributions for three daily time periods and four classes of sky conditions within four approximately monthly periods were calculated and compared. Radiation from a sunny-bright sky over the noon period gave a representative average and would be a reasonable standard sun-sky spectral distribution for comparison with artificial light sources. The relative spectral distribution of xenon-arc radiation in combination with various filters was monitored using the same spectrographic equipment. Comparison of the sun-sky spectral distribution with the xenon arc emission spectrum indicated that although agreement of the lower cut-off wavelength could be attained using Q/Q/WG filters. Xenon radiation was deficient above 3150 Å regardless of the filter system used. Infrared filters removed an undesirable amount of high energy radiation and would be likely to decelerate degradation.

The complexes [Os(NH3)5X]X2, cis-[Os(NH3)4X2]X, and trans-[Os(NH3)4X2]X (X = Cl, Br, I) have been prepared and their infrared spectra measured between 4000–150 cm−1 Assignments have been made for the observed absorption bands. The electronic spectra of the complexes were measured and compared with those of the analogous ruthenium(III) species.

The lifetimes and intensities of positrons annihilating in polyisobutylene were determined over a temperature range from − 100 °C through its glass transition to + 20 °C. The glass transition was determined to occur at − 70 °C compared with a value of − 63 °C determined by differential scanning calorimetry. The intermediate and long lifetimes are concluded to be associated with positrons annihilating in the ordered and amorphous regions, respectively, of the polyisobutylene sample usually considered to be completely amorphous under normal conditions. Depending upon the thermal history, it was determined that between 40 and 50% of the polyisobutylene molecules are aligned in some manner at room temperature. This is to be compared with about 30% in cis 1–2 polybutadiene at the same temperature. The existence of this significant amount of structure in polyisobutylene is offered as an explanation for the sluggish response of butyl rubber to stress even at temperatures 80–90 °C above Tg.

Rayleigh‐Brillouin light‐scattering studies have been carried out on atactic polyethylmethacrylate thermally polymerized under vacuum from extremely clean monomer. The scattered intensity ratio for the VV polarization geometry varies from 2 (at high temperatures) to 5 and appears to be a function of T−1 with a broad discontinuity in the temperature range 40–70 °C. Depolarization intensities have also been measured and, in particular, it is found that ρH equals unity. These results agree with those previously obtained for polybutylmethacrylate and are also compared with reports on polystyrene. Other characteristics of this glass are discussed.

Photon correlation spectroscopy is employed to study the slowly relaxing density and anisotropy fluctuations in bulk atactic polystyrene as a function of pressure at 146 °C from 1 bar to 1.33 kbar. The light scattering relaxation function observed as a function of pressure is identical in shape to that observed previously as a function of temperature. The average relaxation time changes by nearly 4 decades per kbar as the polystyrene sample approaches the glass transition along the isothermal path. The present results represent the first step in the study of light scattering under high pressure near the glass transition in polymers.

New results for positron lifetimes in liquid argon confirm earlier results of Paul and of Liu and Roberts. In particular the orthopositronium intensity is anomalously low in this liquid, only 7%. It is shown by experiment that the high singlet positronium and intensity found by Briscoe, Choi, and Stewart could have been due to oxygen impurity.

In solid polymers the mean lifetime τ2 of ortho‐positronium annihilating by pickoff depends upon the free volume. τ2 has been measured for five samples of relatively monodisperse atactic polystyrene over a temperature range from room temperature to 120°C. The number average molecular weight of the samples ranged from 50 100 to 640 000. For each sample the variation of τ2 with temperature indicated a glass transition about 13 deg below that measured on a differential scanning colorimeter. An increase in the glass transition temperature with molecular weight was observed. The τ2 lifetime, which depends upon the overlap of the positron component of the ortho‐positronium atom with the lattice wavefunction, seems to be very sensitive to the cooperative motion about the chain axis which is associated with the glass transition.

The technique of depolarized Rayleigh light scattering spectroscopy has been applied to follow the kinetics of the thermal polymerization of styrene. By measuring the spectrum of the depolarized scattered light we are able to separate the intensity of light scattered by the polymer being formed from the intensity of light scattered by the monomer. The spectrum consists of a wide Lorentzian due to the monomer and a central spike with instrumental width due to the polymer. This separation occurs because the polymer relaxation time which is determined by the longest Rouse–Zimm mode or by overall rotation is four orders of magnitude longer than the relaxation time of the monomer which is governed by overall rotation. Using the intensity data, the initial rate of the polymerization reaction is measured and is found to agree with the rate determined in previous experiments using classical techniques. After about one‐third of the reaction is complete, the rate increases by 50%. This increase in rate is interpret...