Stretching and deformation vibrations of CH2, C(CH3) and O(CH3) groups of poly(methyl methacrylate)

Schneider, Bohdan; Štokr, J.; Schmidt, Pavel; Mihailov, M.; Dirlikov, S.; Peeva, N.

doi:10.1016/0032-3861(79)90244-1

“…Since the peak intensities and absorption frequencies are very similar in both IR and Raman spectra for both iso-PMMA and syn-PMMA, we have used the same peak assignments for both tacticities. 48,54 Table 1 shows that the peaks for methylene, α-methyl, and ester-methyl groups are very close to each other. Therefore, to help in identifying the origin of the peaks in the SFG spectra, we have also collected SFG spectra for partially deuterated PMMA: d 5 -and d 3 -PMMA (Figure 2).…”

Section: ■ Results and Discussionmentioning

confidence: 80%

Molecular Structure of Poly(methyl methacrylate) Surface II: Effect of Stereoregularity Examined through All-Atom Molecular Dynamics

Jha

¹

,

Zhu

²

,

Dhinojwala

³

et al. 2014

View full text Add to dashboard Cite

The chemical composition and molecular structure of polymeric surfaces are important in understanding wetting, adhesion, and friction. Here, we combine interfacesensitive sum frequency generation spectroscopy (SFG), allatom molecular dynamics (MD) simulations, and ab initio calculations to understand the composition and the orientation of chemical groups on poly(methyl methacrylate) (PMMA) surface as a function of tacticity and temperature. The SFG spectral features for isotactic and syndiotactic PMMA surfaces are similar, and the dominant peak in the spectra corresponds to the ester-methyl groups. The SFG spectra for solid and melt states are very similar for both syndiotactic and isotactic PMMA. In comparison, the MD simulation results show that both the ester-methyl and the α-methyl groups of syndiotactic-PMMA are ordered and tilted toward the surface normal. For the isotactic-PMMA, the α-methyl groups are less ordered compared to their ester-methyl groups. The backbone methylene groups have a broad angular distribution and are disordered, independent of tacticity and temperature. We have compared the SFG results with theoretical spectra calculated using MD simulations and ab initio calculations. Our analysis shows that the weaker intensity of α-methyl groups in SFG spectra is due to a combination of smaller molecular hyperpolarizability, lower ordering, and lower surface number density. This work highlights the importance of combining SFG spectroscopy with MD simulations and ab initio calculations in understanding polymer surfaces. ■ INTRODUCTIONOne of the simplest and still commonly used technique to characterize surfaces of polymers is the measurement of water contact angle. Although this is a very simple technique to judge the wettability of surfaces, it lacks molecular level sensitivity to identify the chemical composition and molecular structure of surfaces. In addition, the rearrangement of molecules at the surface after exposure to water complicates the interpretation of contact angle results. 1 X-ray photoelectron spectroscopy (XPS), a vacuum-based technique, provides excellent information regarding the elemental composition present at the surfaces. However, to identify different hydrocarbon groups (or bondings) is not trivial and relies on subtle shifts of carbon binding energies in the high-resolution XPS analysis. 2 Attenuated-total-reflectance infrared can be used to pick up molecular fingerprints, but this technique samples a much thicker layer than the surface region that affects wetting, surface energy, and friction. 3 In the past two decades, surface-sensitive infrared−visible sum frequency generation spectroscopy (SFG) has been used to study polymer surfaces, 4−7 polymer/liquid interfaces, 7−11 polymer/metal or metal oxide interfaces, 5,12−15 and polymer/polymer interfaces. 12,16−19 SFG is a second-order nonlinear optical technique, and under electric dipole approximation, the SFG signal is only generated by the ordered molecules at surfaces or interfaces and the contribution from ...

show abstract

“…However, the two degenerate asymmetric vibrations assignments are still not resolved based on the IR and Raman measurements. 48,49,51 We have assigned them to be 2990 and 3016 cm −1 based on SFG results. 6,53 The methylene symmetric and asymmetric vibrations are assigned to 2930 and 2960 cm −1 , respectively.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

Zhu

¹

,

Jha

²

,

Bhatta

³

et al. 2014

View full text Add to dashboard Cite

The chemical composition and molecular structure of polymeric surfaces are important in understanding wetting, adhesion, and friction. Here, we combine interfacesensitive sum frequency generation spectroscopy (SFG), allatom molecular dynamics (MD) simulations, and ab initio calculations to understand the composition and the orientation of chemical groups on poly(methyl methacrylate) (PMMA) surface as a function of tacticity and temperature. The SFG spectral features for isotactic and syndiotactic PMMA surfaces are similar, and the dominant peak in the spectra corresponds to the ester-methyl groups. The SFG spectra for solid and melt states are very similar for both syndiotactic and isotactic PMMA. In comparison, the MD simulation results show that both the ester-methyl and the α-methyl groups of syndiotactic-PMMA are ordered and tilted toward the surface normal. For the isotactic-PMMA, the α-methyl groups are less ordered compared to their ester-methyl groups. The backbone methylene groups have a broad angular distribution and are disordered, independent of tacticity and temperature. We have compared the SFG results with theoretical spectra calculated using MD simulations and ab initio calculations. Our analysis shows that the weaker intensity of α-methyl groups in SFG spectra is due to a combination of smaller molecular hyperpolarizability, lower ordering, and lower surface number density. This work highlights the importance of combining SFG spectroscopy with MD simulations and ab initio calculations in understanding polymer surfaces. ■ INTRODUCTIONOne of the simplest and still commonly used technique to characterize surfaces of polymers is the measurement of water contact angle. Although this is a very simple technique to judge the wettability of surfaces, it lacks molecular level sensitivity to identify the chemical composition and molecular structure of surfaces. In addition, the rearrangement of molecules at the surface after exposure to water complicates the interpretation of contact angle results. 1 X-ray photoelectron spectroscopy (XPS), a vacuum-based technique, provides excellent information regarding the elemental composition present at the surfaces. However, to identify different hydrocarbon groups (or bondings) is not trivial and relies on subtle shifts of carbon binding energies in the high-resolution XPS analysis. 2 Attenuated-total-reflectance infrared can be used to pick up molecular fingerprints, but this technique samples a much thicker layer than the surface region that affects wetting, surface energy, and friction. 3 In the past two decades, surface-sensitive infrared−visible sum frequency generation spectroscopy (SFG) has been used to study polymer surfaces, 4−7 polymer/liquid interfaces, 7−11 polymer/metal or metal oxide interfaces, 5,12−15 and polymer/polymer interfaces. 12,16−19 SFG is a second-order nonlinear optical technique, and under electric dipole approximation, the SFG signal is only generated by the ordered molecules at surfaces or interfaces and the contribution from ...

show abstract

“…The vertical lines correspond to the varying IR absorption bands during recovery as assigned in Figure 14. α represents the first carbon atom that is attached to the functional group COOCH 3 ) and (O)CH 3 strongly overlap around the band at 1450 cm -1 [102,103,107]. The peak at 1485 cm -1 can be assigned to the α-CH 3 asymmetric deformation vibration of PMMA [102,103,107].…”

Section: Ftir Resultsmentioning

confidence: 99%

“…α represents the first carbon atom that is attached to the functional group COOCH 3 ) and (O)CH 3 strongly overlap around the band at 1450 cm -1 [102,103,107]. The peak at 1485 cm -1 can be assigned to the α-CH 3 asymmetric deformation vibration of PMMA [102,103,107]. While the peak at 1136 cm -1 may be a new peak, it might also be the result of a frequency shift of the 1150 cm -1 peak under irradiation that recovers after the laser is turned off.…”

Section: Ftir Resultsmentioning

confidence: 99%

Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

Hung

¹

,

Bhuyan

²

,

Schademan

³

et al. 2016

The Journal of Chemical Physics

View full text Add to dashboard Cite

The mechanism of reversible photodegradation of 1-substituted aminoanthraquinones doped into poly(methyl methacrylate) and polystyrene is investigated. Time-dependent density functional theory is employed to predict the transition energies and corresponding oscillator strengths of the proposed reversibly-and irreversibly-damaged dye species. Ultraviolet-visible and Fourier transform infrared (FTIR) spectroscopy are used to characterize which species are present. FTIR spectroscopy indicates that both dye and polymer undergo reversible photodegradation when irradiated with a visible laser. These findings suggest that photodegradation of 1-substituted aminoanthraquinones doped in polymers originates from interactions between dyes and photoinduced thermally-degraded polymers, and the metastable product may recover or further degrade irreversibly. INTRODUCTIONOrganic materials have a broad range of applications such as high-resolution fluorescence microscopy [1][2][3][4][5][6][7], second harmonic generation (SHG) microscopy [8][9][10][11][12], dye sensitized and polymer solar cells [13][14][15][16][17], solid state dye/organic lasers [18][19][20], and organic light emitting diodes [21,22], to name a few. Photostability of organic compounds and polymers is often a requirement for applications incorporating light-matter interaction [2-4, 6, 8, 18-20, 23-30]. When a material undergoes photodegradation, its characteristic properties deteriorate over time, which is referred to as decay; the reverse change in the characteristic properties of the material is referred to as recovery. Though photodegradation is often irreversible, the recovery process has been observed from a large variety of materials, typically involving polymers and often together with dyes, with various experimental techniques when the photodegraded materials are kept in dark for a long enough time, typically hours to days [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44].Amplified spontaneous emission (ASE) of disperse orange 11 (DO11) doped in poly(methyl methacrylate) (PMMA) bulk sample was observed to fully recover in the dark about 40 hours after photodegradation when irradiated with a 532 nm second harmonic Nd:YAG picosecond laser [33]. This self-healing phenomenon was also observed in various anthraquinone derivatives doped in PMMA and polystyrene (PS) thin films [41,42] and DO11 doped in MMA-styrene copolymers thin films [42,45] probed with transmittance image microscopy and ASE. The photodegraded thin film samples are often observed to recover partially, which suggests there exists both reversible and irreversible photodegradation. The lack of evidence for linear dichroism during photodegradation measurements eliminates orientational hole burning as the mechanism causing reversible photodegra- [38,42,46,[50][51][52][53][54], they have failed to elucidate the underlying mechanism.Several hypotheses of the mechanism responsible for reversible photodegradation in DO11/PMMA have been proposed, including intramolecular proton transfer and ...

show abstract

Stretching and deformation vibrations of CH2, C(CH3) and O(CH3) groups of poly(methyl methacrylate)

Cited by 87 publications

References 12 publications

Molecular Structure of Poly(methyl methacrylate) Surface II: Effect of Stereoregularity Examined through All-Atom Molecular Dynamics

Molecular Structure of Poly(methyl methacrylate) Surface II: Effect of Stereoregularity Examined through All-Atom Molecular Dynamics

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

Contact Info

Product

Resources

About