Matrix Assisted Laser Desorption Ionization–Time of Flight (MALDI-TOF) mass spectroscopy is used in the characterization of synthetic polymers. MALDI allows for determination of: modal, most probable peak (MP), molecular number average (MN), molecular weight average (MW), polydispersity (PD), and polymer spread (PSP). We evaluate a new sample preparation method using Induction Based Fluidics (IBF) to kinetically launch and direct nanoliter volumes to a target without contact. IBF offers signal improvement via field enhanced crystallization. This is the first study to discuss filed enhanced crystallization in MALDI sample preparation. IBF can increase signal/noise (S/N) and signal intensity for polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(ethylene glycol) (PEG) across a mass range of 2,500 to 92,000 Da showing more accurate PSP. Increases in S/N range up to: 279% for PS, 140% for PMMA, and 660% for PEG. Signal intensities increased up to: 438% for PS, 115% for PMMA, and 166% for PEG. Cross-polarization microscopy indicates dramatic morphology differences between IBF and micropipette. Finally, we speculate as to why IBF nanoliter depositions afford higher S/N values in experiments conducted in different instrumental configurations even without optimization.
Next we sought to investigate whether nanoliter volumes of concentrated polar liquids and organic monomers launched to targets using IBF can be verified through the real time charge measurements. We show that using a nanoliter IBF dispensing device and nanocoulomb meter, charge measurements made on nanoliter drops in real time are correlated with the droplets surface area following Gauss's Law. We infer the "induction only" formation of the double layer showing the ability to determine nanoliter volumes, nearly instantaneously, in real time. Implications are presented from these IBF measurement observations on improving/monitoring MALDI quantitation and its quality control.
Polymer-dye interactions were further investigated using PMMA composites made from a polar metalloporphyrin [5-(4',4',5',5'-tetramethyl[1',3',2']dioxaborolan-2'-yl)-10,20-diphenylporphyrinato]zinc(II) (Zn(II)Bpin-DPP) in select weight %s (wt%s). Fluorescence spectroscopy has revealed that the porphyrin was well dispersed within the composite. Differential Scanning Calorimetry (DSC) showed that porphyrin acted as an antiplasticizer raising the glass transition (Tg) from 105°C to 123°C. Dielectric Analysis (DEA) was performed in the frequency range of 0.3 Hz to 100 kHz between - 150 to 270°C. Permittivity (ϵ'), loss factor (ϵ'') and dielectric response of beta (β), alpha beta (αβ), and conductivity relaxations were studied. Previous DEA data was limited to 190°C. This study brings analysis to 270°C which is start point for the first part of PMMA degradation. Thus forwarding DEA can be used to evaluate PMMA degradation. The electric modulus formalism is used to reveal the β and conductivity relaxations. The apparent activation energies (Ea) for the molecular relaxations are presented. AC (σAC) and DC (σ DC) conductivity are also evaluated. Tan delta (δ), dissipation factor, evaluated between 1 Hz to 100 kHz was shown to increase with porphyrin loading although locally affected by free volume restriction. Havriliak-Negami (H-N) equation was fit using the complex electric modulus (M*) modified form and was performed on the conductivity region 160 to 190°C and degradation region 190 to 270°C. Relaxations above the Tg were proven to be conductivity relaxations using four proofs. This is the first study to investigate PMMA degradation DEA with the complex electric modulus, M*,revealing a unique occurrence of increasing central relaxation times (s-1) and reducing electric loss modulus (M'') frequency maxima (Hz) after the degradation temperature of 220°C was reached supporting current literature of the first of a two part degradation process that proceeds via end chain scission.
|Advisor:||Harmon, Julie P., Malik, Abdul|
|Commitee:||Crane, Nathan, Li, Xaio, McLaughlin, Mark L.|
|School:||University of South Florida|
|School Location:||United States -- Florida|
|Source:||DAI-B 71/12, Dissertation Abstracts International|
|Subjects:||Analytical chemistry, Organic chemistry, Polymer chemistry|
|Keywords:||Dielectric analysis (dea), Dye-polymer, Electric modulus, Electric-field, Induction based fluidics (ibf), Poly(methyl methacrylate) (pmma)|
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