Photon correlation spectroscopy of bulk poly(n‐hexyl methacrylate) near the glass transition

Hwang, Yeongwoo; Patterson, G. D.; Stevens, J. R.

doi:10.1002/(sici)1099-0488(199610)34:14<2291::aid-polb1>3.3.co;2-7

Cited by 2 publications

(9 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…7 Hwang found that the parameter varied between 0.21 and 0.43 over the temperature range from 10 to 36 8C. 3 In the current studies, the parameter is weakly temperature dependent over the experimental temperature range.…”

Section: Photon Correlation Spectroscopymentioning

confidence: 43%

“…Three previous studies of the light scattering from PHMA have been published, but they exhibit conflicting results. 3,7,18 To study the full range of relaxation behavior and improve the analysis of light scattering relaxation functions in PHMA, an optically perfect sample is necessary and the experimental data must be more refined. Herein we report the RBS and PCS from an optically pure sample of PHMA.…”

Section: Cðtþ ¼mentioning

confidence: 99%

“…The relaxation functions for poly (alkylmethacrylates) are highly nonexponential. 3,5,38 Initial analysis represented the relaxation function as a stretched exponential function (eq 18). 31,39 This form of the relaxation function is fit to four parameters; o , , amplitude, and a variable baseline.…”

Section: Photon Correlation Spectroscopymentioning

confidence: 99%

“…Meier reports an LPR of 8 at 50 8C, 18 and Hwang reports an LPR of 2.3 at 25 8C for PHMA. 3 This increase relative to the intrinsic value is a result of impurities in the sample that give rise to light scattering that does not come solely from longitudinal density fluctuations. The present sample has an LPR of 1.3 at 0 8C, a lower value than any PAMA studied previously near the glass temperature.…”

Section: Rayleigh-brillouin Spectroscopymentioning

confidence: 99%

“…2 Light scattering has been employed to study the time dependence of density fluctuations for many poly(alkyl methacrylates) (PAMAs) near the glass transition. [3][4][5][6][7][8] Two different experiments allow for the study of different time scales. Rayleigh-Brillouin spectroscopy (RBS) can be used to study fast relaxation processes on the order of nanoseconds, while photon correlation spectroscopy (PCS) is used to measure slower relaxation processes.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Evidence for the γ‐relaxation in the light scattering spectra of poly (n‐hexyl methacrylate) near the glass transition

Savin

Patterson

Stevens

2005

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

The full range of relaxation processes present in optically pure poly-(n-hexyl methacrylate) (PHMA) was studied using Rayleigh-Brillouin and photon correlation spectroscopy (PCS). Brillouin shifts, linewidths, and Landau-Placzek ratios (LPR) were measured over the temperature range from À11 to 21 8C. The Brillouin splitting and linewidth were consistent with previous studies of PHMA, but the LPR was much lower, indicating that the scattered light primarily comes from intrinsic density fluctuations. Relaxation functions of the same PHMA sample were measured using PCS over the temperature range 0.5-52.5 8C. The average relaxation times calculated from a Williams-Watts fit follow a VFT temperature dependence, with the stretching parameter decreasing with decreasing temperature. The distribution of relaxation times reveals a merging of the and -relaxations over this temperature range, and the temperature dependent width confirms that there are at least two processes with separate temperature dependences. Furthermore, there appears a process at short times in the correlation function window at low temperatures. This upturn at the fastest relaxation times is attributed to the -relaxation present in higher order methacrylate polymers. The effect of the -relaxation is discussed in terms of the dynamic behavior over 12 decades in time. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1504-1519, 2005

show abstract

Section: Photon Correlation Spectroscopymentioning

confidence: 43%

Section: Cðtþ ¼mentioning

confidence: 99%

Section: Photon Correlation Spectroscopymentioning

confidence: 99%

Section: Rayleigh-brillouin Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evidence for the γ‐relaxation in the light scattering spectra of poly (n‐hexyl methacrylate) near the glass transition

Savin

Patterson

Stevens

2005

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

show abstract

Segmental Dynamics and Density Fluctuations in Polymer Networks during Chemical Vitrification

Fitz¹,

Mijović²

1999

Macromolecules

View full text Add to dashboard Cite

Molecular dynamics of network-forming reactive polymers were examined as a function of the advancement of chemical reaction as the materials structure undergoes a transition from liquid to amorphous solid. The accompanying changes in the segmental relaxation time (α process) are a signature of the materials state (within the liquid to amorphous solid spectrum of physical properties). Both broad-band dielectric relaxation spectroscopy (DRS), which probes the α process via dipolar reorientational mobility, and dynamic light scattering (DLS), which probes the α process via density fluctuations, were used to monitor the system under reaction conditions in the reaction bath (to our knowledge, the first study of its kind). An excellent agreement was found between DRS and DLS for the α process characteristic parameters: relaxation time and KWW, the stretched exponential parameter (characterizing the relaxation breadth). That dipole dynamics exhibit the same α relaxation characteristics as time dependent density fluctuations, suggests that the rotational motion observed in a DRS measurement is directly controlled by the behavior of the density domains. It was concluded that the broadening of the α process is due to a general phenomenon: the micro/nanoscale heterogeneous nature of glass formers. The results of the study are discussed in terms of cooperative and local relaxation modes in the growing network.

show abstract

Photon correlation spectroscopy of bulk poly(n‐hexyl methacrylate) near the glass transition

Cited by 2 publications

References 0 publications

Evidence for the γ‐relaxation in the light scattering spectra of poly (n‐hexyl methacrylate) near the glass transition

Evidence for the γ‐relaxation in the light scattering spectra of poly (n‐hexyl methacrylate) near the glass transition

Segmental Dynamics and Density Fluctuations in Polymer Networks during Chemical Vitrification

Contact Info

Product

Resources

About