Degradation of Polymers

Long LorChem 4101 Fall 2010December 13, 2010

Polymers• Polymers are large

macromolecules containing two end groups and longs chains of repeat units.

• They are often derived from petroleum

• Billions of kgs of polymers are produced annually. In the 1990, production close to 150kg of polymer per person in US

• Degradation of polymers is done by use of UV light, Ozone cracking, hydrolysis, and heat.

Analyte

• Styrene is derived from petroleum, performing alkylation of ethylene and benzene

• Production of polystyrene in the US and Canada is approximately 2.2 billion kgs

• The molecular weight, mw, of PS will depend on the original purpose– Avg. mw range: 103 -106 g/mol

• Repeat unit: 104.15g/mol

Experimental

• Problem: The world relies heavily on fossil fuels. Polymers, in certain conditions, will depolymerize back into monomer. Could we use this process to get enough monomer to perform another polymerization.

• Hypothesis: Detection of polymer degradation back into monomer is quantifiable using proton NMR or IR.

Relevance of Problem

The energy crisis over recent years has become more evident, its clear that we humans have relied on consuming fossil fuels for everything. There have been recent developments in other areas, such as solar technology, but that is still a ways away. The use of petroleum based materials in polymers is something that this analytical problem hopes to address. Upon detecting the depolymerization of polymer back to monomer, there will less consumption of fossil fuel.

Techniques consideredTechnique Advantages Disadvantages

SEC (GPC) Well defined separation timeHigh molecular weight detection

Requires 10% Mw differencePrior filtration required

GC-MS Low LOD, about 0.25pg Higher Temperature to make gas stateHigh cost

ESI-MS Detects high molecular weights > 100,000Da

Does not handle Matrix wellDifficult to clean

HPLC-MS Low LODGradient solvent system

Excess solvent gas when changing over to MS detector

MALDI-TOF

Advantages• Can separate high mw

compounds• Low sample concentration

– Femto mol concentrations

• Low background noise• Selective mass charge

analysis• Multiple sample

analysis

Disadvantages• Standards are required for

MALDI• Limited mass range• Relative Instrument cost

Instrument

LaserToF LT3 Plus• Laser – Pulsed UV 337nm

Nitrogen• Mass accuracy – 20ppm• Mass range > 500000 Da.• Sensitivity < 1femtomol• Large dynamic and linear

range• Cost around $28000-35000

Sample preparation

• Obtain possible degradation samples of polystrene

• MALDI requires that there be a standard to compare to.– Styrene standard would be

used• ProteoMass™ Aldolase

– (39.2 kDa)

• Load samples into LaserToF and run sample

Expected results

An example of MS spectrum for MALDI-ToF, M.W. 2.3kDa

• If the degradation of polystyrene to monomer styrene occurred, there would be two peaks that separate Gaussian peaks– Styrene at low m/z– Polystyrene at high m/z

• Although not quanitative in the approach, this technique will the extent of depolymerization.

Conclusion

• The analysis of degradation of styrene from polystyrene using the MALDI-TOF technique, the technique will provide sufficient separate peaks representing the degradation of polystyrene.

• If separation is efficient enough, further analysis of degradation can be determined qualitatively for use in obtaining monomer from recycled polymers.

References• “Degradation of polymer in nature.” Health Envrionment &

Regulatory Affairs (HERA), Dow Corning. Ref # 01-1112-01. 1998, accessed Nov. 2010.

• Katz, David A. “Polymers” 1981, 1998. Accessed Oct 2010.• “Basics of Polystyrene Production” Chemical Engineering

Tools and Information. <http://www.cheresources.com/polystyzz.shtml>

• Young, Sandra. MALDI-TOF MS. http://www.psrc.usm.edu/mauritz/maldi.html

• LaserToF LT3 Plus. Scientific Analysis Instruments. Accessed Dec. 2010. <http://www.saiman.co.uk/laser-tof-lt3-plus.html>