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12th International Conference & Workshop

“Medical Physics in the Baltic States”, 2015

RAMAN SPECTROSCOPY OF

POLYMERIZATION PROCESSES

IN nPAG AND nMAG DOSE

GELS

Neringa VAIČIŪNAITĖ1, Rimas ŠEPERYS2

1 Physics Department, Kaunas University of Technology

2SME “Šeši partneriai”

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INTRODUCTION

• Polymer gels have been proven to be a valuable tool for

determination of beam dose characteristics and 3D radiation

dose measurements for medical purposes [1-3].

• A typical gel dosemeter consists of water, gelatin agent,

monomers and a cross-linker comonomer [4,5].

• Many chemical compositions have been proposed for

dosimetric purposes, but only a few have been carefully tested

[4,5].

• To evaluate the interaction between monomer consumption

and polymer production is very important [6].

AIM OF THE STUDY

The aim of this study was to identify the radiation interaction

mechanisms on photon irradiated nPAG and nMAG polymer

gels in accordance with analysis of characteristic vibrational

modes of dose gel components

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POLYMER GELS PREPARATION

AND IRRADIATION

nPAG nMAG

89% Highly purified water 86% Highly purified water

5% Gelatine 8% Gelatine

3% Acrylaimde 6% Methacrylic acid

3% N; N- methylene-

bisacrylamide

-

10 mmol/l Hydroxymethyl

phosphonium chloride

10 mmol/l Hydroxymethyl

phosphonium chloride

nPAG and nMAG polymer gels were irradiated by

Co60 photon source of teletherapy unit (ROKUS M)

by 2 Gy dose. Dose rate of 0.03 Gy/ min,

SSD – 100 cm, field opening – 10×10 cm. Fig.1. Preparation of the

dose gel.

POLYMER GELS PREPARATION

AND IRRADIATION

Fig. 2. Micro Raman

inVia Renishaw

a)

b)

Micro Raman

(inVia Renishaw)

vibrational

spectroscopy of

the irradiated

copolymerized

nPAG and nMAG

samples in

cuvettes was

performed on the

7th post-irradiation

day.

Fig. 3. a) Non irradiated nPAG

gel, b) Non irradiated nMAG

gel, c) nPAG irradiated by 2

Gy Co-60, d) nMAG irradiated

by 2 Gy Co-60.

a) b) c) d)

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RESULTS AND DISCUSSION

Fig.4. Chemical

structure of

a) acrylamide,

b) polyacrylamide.

a)

b)

Fig.5. Micro -Raman spectra of nPAG polymer dose gel:

a) non irradiated, b) irradiated by 2 Gy by Co60 photon source.

nPAG

a)

b)

RESULTS AND DISCUSSION

Fig.6. Polymer

development observed

in Raman spectra of

normoxic

polyacrylamide (nPAG)

gel in the range of

900-1400 cm-1 and

2800-3200 cm-1.

a), c) Non irradiated

nPAG gel;

b), d) irradiated nPAG

gel.

nPAG

a)

c)

b)

d)

1256

1285

1256

1285

FWHM = 310,9 FWHM = 1229,1

2880

2936

FWHM = 121,7 FWHM = 213,6

2880

2936

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RESULTS AND DISCUSSION

Fig.7. Chemical

structure of a)

methacrylic acid,

b) polymetchacrylic

acid.

a)

b)

a)

b)

Fig. 8. Raman spectra of nMAG polymer dose gel: a) non

irradiated, b) irradiated by 2 Gy by Co60 photon source.

nMAG

RESULTS AND DISCUSSION

Fig. 9. Polymer

development

observed in Raman

spectra of normoxic

methacrylic acid

(nMAG) gel at the

range of 450-600cm-1

and 2000-3200 cm-1.

a), c) Non irradiated

nMAG gel;

b), d) irradiated nMAG

gel.

539

539

2955

3114

2955

3114

a)

b)

c)

d)

FWHM = 111,4 FWHM = 1198,8

FWHM = 102,8 FWHM = 290,7

nMAG

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CONCLUSIONS

• Photon irradiation of Co60 was applied to normoxic nPAG and

nMAG polymer dose gels to perform a polymerization process.

• The Micro-Raman spectra and full-width half-maximum

calculations, showed the incensement of polymer representing

vibrational bands and sharp reduction of monomer fraction.

• The reduction of BIS proved the theory of cross-linker

consumption and its importance in network structure formation.

• The results agreed with the studies of other researchers,

however more tests are needed to evaluate the consumption rate

of monomers and cross-linker.

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Thank You for your attention

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REFERENCES

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Conference Series 56, 2006. p. 35–44, doi:10.1088/1742-6596/56/1/004.

3. De Deene Y. Essential characteristics of polymer gel dosimeters. „Third International

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625 – 629. doi 10.5012/bkcs.2011.32.2.625.

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