Gunasekaran, S

Hemamalini, R

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l„Juw j. Phys. 77B (3), 319-322 (2003)< UP\Spectroscopic analysis on the structure of poly methylmethacrylate (PMMA)S Gunasekaran** and R HcmamalmiDepartment of Physics. Queen Mary's College, Chcnnai-600 004. India ‘ Dcpartincni of Physics, Pachaiyappa's College. Chcnnai-600 010, IndiaE-inuil raj_hema0.K«^rc(liffmail com Received 26 Novemhet 2002, lu iepted J March 200JAhslracl The present work is devoted to the study of ihe structure and potciilial energy distiihuiion ol crystalline PolyMi'ihylincthacrylate(PMMA) A qualitative analysis ol the pare sample of PMMA has been made by a sutislactory vibration band assignment using FTIK aiul Raman spectra. A normal coordinate analysrs has been earned out using the method ol kinetic constants A systematic set of potential jHisLinis have been computed using the method of kinetic constants on the basis ol C symmetry comparing with those ol the related molecules The lioiLnii:jl energy distribution confirms Ihc correctness of the assignments madeKivwnrds Poly methylmethacrylate (PMMA), FTIR and Raman spectra, normal coordinate analysis P\CS Nos. 20 Ea. 3.'l.2().Fb. 33.20 Tp1. IntroductionPMMA IS an glassy polymer commercially called acrylic, with ! an amotphous structure, derived from the monomer methyl i'’lethacrylalc. It is optically active [II with high level of I Msparcncy and an excellent substitute for glass with good Mhanical property. It is one of the hardest thermoplastics and scratch resistant. It is used for making attractive sign Wrds, optical fibers, contact lens, lighting fixtures, window Greens, automobile lighting biological specimen, preservation Ventures, syringes etc. Earlier works reported are on IR studies >^^ iiuiomobile scrapyard. acrylic[2], optical fibre transmission 'ladies using PMMA[3] and non-destructive analysis of photo- ‘^ '^ gradahon of PMMA[4], However, the vibrational spectra of have not been examined thoroughly so far, perhaps due [''J^ hehigh complexity and low symmetry of the monomers.' ihi attempt is made to identify the vibrational frequencies r^ 'Tespanding to each of the functional groups and hence forth I'^ '^ iructural elucidation.spectra was recorded in the range 4000 - 400 cm * using Perkin Elmer spectrophotometer at Medopharm, Chennai, India The Laser Raman spectra in the same wave number range was recorded at RSIC, Chennai using the DILOR Z 24 Raman spectrophotometer. The spectra arc presented in Figures I and2.^Aperimentalsample of Poly Methyl Methacrylate (PMMA) was procured  ^OPET, Chennai. India. The Fourier transform InfraredAuthorFigure 1. FTIR .spectrum of poly methyl methacrylate 3. Normal coordinate analysisThe repealing unit of PMMA belongs to symmetry [5]. The assumed structure of the compound under study is presented in Figure 3.Thc interatomic distances and bond angles were taken from Sutton Tables [6] from related compounds. PMMA has 39 fundamental modes of vibration under point group©2003IACS320 S Gunasekaran and H Hemanialiniand can be rcprcscnied as -2 5 A '  + \4A '" . 0( this, 22F ' i | ; u r c  2.  Las i . ' i  k a i i t a n  s p C L t i u r n  o f  p o l y  i iKMhyl i i i e t h a c r y l a l csymmciric coordinales arc considered here. 14 synimelric co­ordinates are assigned lo A' species and K to A" species. In view ol the symmetry , the monomers of the polymer will have only two types ol vibrations, namely, stretching and bending and will be active in both IR and Raman. On the basis of internal coordinates, A D ,  A 7 , , A d ^ , A L ,  A l^ , A l-^ , A r^ , A n ,  AR^, AR^, AR^, Ali^, Ah^^ Ahy, A<I^^ , A 0 j ^  A 0 ^ ,A6^, AO^, A6^^,A(Q2 . Aco^ , Al]^, ^ ^ 2 ' and arcthe orihononnal set of symmetric coordinates constructed for in plane and out of plane vibraiionsf7,81 that arc used in the present work. A normal coordinate analysis has been carried out using the method of kinetic constanis[9-l 1 J.Thc symmetric coordinates are listed below :A ' species:S^=AD, S 2= 0 /^ f2 ) (A d^+ A i2 ) ,  S^=AL, s,r. ( I /V 2 H 4 / ,+ 4 /2 ), 5, = 4 a ,  5^ , = (1 / V 2K 4y, + j y ,,S-j = A\i/, Sf^  = ( \ I  yf i) (AJti + AR2 + AR^), i ' i ,= ( | / / i ,(A f i ^A h 2 A h -^ ) , S]Q = Ay^,{A0^-^A024‘A0^), 5 i2 = (1 / V3) (^ 77, -^Arj, +A;]. 15 ,,= (1 /V 2 ) (^ / ',+ ^ /2 ) ’ i ’,4 =(l/y2)(zi<^,+a^;>)A ” species := (1 /7 2 ) (4 4 |-4 ^ /2 ) ,  5 ,6 = (1 /V 2 ) (4 / |- 4 / , ) ,  -V, (1 /V 2 )(4 y , +Ay 2). 5 |h = ( I /V 6 ) ( 2 4 e , -A B .+  W -iS|(; = ( I / V6) (24^1 — 4/?2 "t" 4^^), 5t() = (I / v(' '(24yj|- 4/12 + 4 /1^ ), i ’,| = (l/> /2) (4(*,- 4 ^ , ) -3.! IR and Raman vibrational band assignment:The C-H asymmetric stretching of methyl and mcthyleiK' rroup' are expected to occur in the range 3100-2950 cm ' and syiiimciiK strctching[ 12| between 2900-2840 cm In P M M A  ih i  symmetric stretching vibrations are assigned to ihe baml^  ai 1 2837,2855 and 2867 cm ' forIRand.2839 and 2880cm ' lui Rmui j and asymmetric stretchings at the same values 101 holli (In j spectra i.e., at 2905 and 2945 cm '. The symmetric vibraiu appear to be intense. In PMMA, most of the IR and Ramu bands are found at about the same values, the C-C sircklmu' occurs well at the expected value, i.e., symmetric strclclmiii a 967 cm‘' and asymmetric stretching at 1087 cm’' 113] The I I f  ^* bending vibrations is expected at 1160 cm ' for the hydnko substituted ethylene compounds! 14]. The vibrations ai cm ' may be due to this bcnding.The methylene bending nccui'' with high intensity at 1370^cm' 115] . The CCC deformaiiun vibration [ 15] is observed for PMMA at 755 and 864 cm ' 1 symmetric deformation vibration of CCO is observed ai  cm ' and asymmetric at 721 cm ' .This however has occurrol bli­the expected value [14]. The C-O symmetric and asyinmcinj stretching vibrations [ 14J occur between 1030-1200cni' case of di and tri substituted ethane compounds, the b a n d s  1045 cm*' and 1118 cm ' are assigned to the symmetric a asymmetric C-O stretching vibrations.3.2 Computational method :A computational procedure is developed to find the B Matrix  ^Matrix and then the K matrix as the inverse of the G matrix using Gauss- Jordon algorithm! 16].The Crout algorilhml I^ l' modified to evaluate the determinant value ofmatrix. For different the corresponding F , are obiaincJ’Spectroscopic analysis on the structure of pol\ methylmethacrylate (PMMA)Table 1. Normal inodes of vibruuon, poicniial consianis and PED of poly meihyl incihacrylaie321FundamentalmodesFrequencies cm 'V, (A’)V. (A') v'l (A')>4 (A')(A')‘■f, (A')7^ (A)V, (A') Vy (A') v,o (A') V,, (A')1^2 (A )' L l  ( A ' )'14 (A')»'is (A”) 'u, (A")Vi7 (A")'-IH <A") v,y (A") ':o (A") '^ 21 ^A )v't 1 (A )FTIR Laser Raman AssignmentPotential constants ( l ( ) ‘ N / m )9 6 7  ( s )  1010 ts) 1 7 3 0  ( v s )  1 0 4 .S  ( s )  1 3 7 0  ( s )7 5  5 ( s )6 5 0  ( m s )  2 8 3 7  ( v s )  2 8 5 5  ( v s )  8 2 0  ( s )  1 3 8 5  ( s )I 1 4 0  ( v s )  2 8 6 7  ( v s )  5 7 9  ( s )  1 0 8 7  ( s )  1 1 1 8  ( s )  8 6 4  ( s )  1 5 2 5  ( v s )  2 9 0 5  ( m s )  2 9 4 5  ( s )  7 2 1  ( v s )  6 0 5  ( s )9 7 0  ( m s )1 7 7 0  ( m s )  1 0 5 5  ( w )7 5 4  ( i n s )  6 5 0  ( s )  2 8 ^ 9  ( m s )8 0 8  ( m s )1 1 7 7  ( s )9 0 0  ( m s )  1 5 6 0  ( s )  2 9 0 3  ( m s )  2 9 4 5  ( s )  7 0 0  ( w )  6 0 0  ( w )c-cc-cr, C=0 C-O CH,6^ CCC 6 COC CH, n i ,  CCC HCH 5 OCH r, C-ll OCC C-C C-O CCC CH, C-H 'uu C-H OCC OCO6 8 1 3 8  6 8 1 4 3  6 6 7 5 6  6 3 2 4 7  0 5 1 4 0  0  5 0 6 3  0  5 2 1 9  5 8 7 2 25 8 7 1 6  0  5 0 7 0  0 5161 0  4 9 2 8  5 . 8 7 3 2  0 4 9 5 7  6 . 2 7 4 46 275  ^0  5 0 8 1  0  4 9 2 8  4  3 4 2 5  4  3 4 5 6  0  4 9 5 7  0  4 8 2 4PEO %9 99 7  5 2  9 6  8 5  4 2  409 8  9 8  4 84 0  569 84 19 9  9  8 4 4  99 9 3  9 3404 1w-weak, ms -medium strong . s-strong. vs-very strongV^ilson's approximation[ 181-PED is calculated using the relation PEI) = F^j I k j  . The frequencies of PMMA observed inIR and Raman spectra with their relative intensities and probable assignments of fundamental modes are summarized in 1 along with a reliable set of potential constants and PED'■‘^ Iculiuion.Conclusion^‘>aiislactory vibrational band assignment has been made '^^ iliiblc for poly methyl methacrylate through Infrared and [4j spectral measurements. A systematic set of potential ^^’^ 5ianis have been computed using the method of kinetic on the basis of symmetry. To check whether the SCI of symmetric coordinates contribute maximum to the energy associated with the normal coordinates of the "^ ^^ ecules, the potential energy distribution has been carriedout. The poienlial energy distribution for all the methyl and methylene stretching and bending modes were found to be especially very satisfactory! 19].R eferencesMl121[31Prachi Pandey and A K Snvastava Advances in Polym er tedm olo f;\ 21 1, 59 (2002)Patrick Hcndra and Peter Mucci Int J Vib.Spect 1 4. 45 (1997) A Olinga, R Win/en, H Rehage and H W Sieslcr J Near Infrared SpecirosL 9 19 (2001)M Shirnoyama, K Matsukawa, H Inoue, T Nmomiyaa and Y Ozaki J. Near Infrared Spectrosc 7 27 (1999)[5] N B Colthup, L H Daily and S E Wibcrly Introduction to Inftared and Raman Spectroscopy (New York . Academic) (1990)[61 L E Sutton The Interatomic Bond and Bond Angles in Molecules and Ions (Chemical Society, London) (1956)[7J Y Marino, K Kutchitsu and T Shimanouchi J Chem. Phys 120 726 (1952)322 S Gunasekaran and R Heniamalini(81 13 E Mann, T Shimanouchi, J H Mean and L Fano J Chem Rhy\27 43 (1957)[9 1 P Thirugnanasambandain and S Mohan J Chem Phy.\ 61 470 (1974)(10| S Mohan and S Gunasekaran ./ Chem /Viva Ml 225 (1984)111] S Gunasekaran, K Manoharan, P Kumaresan and S Mohan Amuh J Chem Phvs 6 82 (1994)(121 Kmimi. C Y Liang and G B H M Sutherland J Chem /Vjv.v 25 549 (1956)(13| Silvcrstcin et al, Spenritst Id e n iifn a h o n  of O r^anu  Compoiimh (Tourlh edition) Nl-w York John Wiley (1991)(141 John Dyer Application of Absorption Spectroscopy of Compounds (New Delhi . Prcniice Hall of India) (1987)115] R A Meikleiohn Anal Chem 29 329 (1957)(161 M Rathnakuman Fh. D Thesis (University of Madras, ln,j, (1995)(17] H William Numerical Recipes in Fortran. The Art of Sunmfi Computing (New Delhi ■ Cambndge University Press) p 3(,(181 E B Wilson Jr, D C 13ccius and P C Cross Molecular Vihiain„u (New York McGraw-Hill) (1995)1191 P Venkata Rainana Rao Fh D Thesis (Kakatiya Univcrsii>, imJij: (1988)

Spectroscopic Analysis on the Structure of Poly Methylmethacrylate (PMMA)

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Spectroscopic Analysis on the Structure of Poly Methylmethacrylate (PMMA)

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