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In Situ Polymerization

Figure 1: In Situ Polymerization of microcapsule-imbedded nanoparticles to yield polymer nanocomposite product (Source: Wikimedia Commons)

-              This figure will add to the article by giving a better visualization of the actual in situ polymerization process

I. Introduction

·            In polymer chemistry…

o  Preparation method to develop polymer nanocomposites (chemical encapsulation technique)

·            Steps involved

o  Dispersion of nanoparticles[1]

o  Initiation by heat/radiation[1]

o  End product = polymer nanocomposite[1]

·            Conditions required

o  Low viscosity pre-polymers[1]

o  Short period of polymerization[1]

o  Requires polymer with good mechanical properties[1]

o  No side products[1]

·            Advantages

o  Cost-effective materials[1]

o  Easy to automate[1]

o  Can integrate with many other heating and curing methods[1]

·            Disadvantages

o  Limited usable materials[1]

o  Short time period to execute process[1]

o  Expensive equipment[1]

·            Polymer Nanocomposites

·            Have components on a nanoscale level

·            Two types

o  Biomolecule-linear polymer hybrids[2]

§ Covalent bonds between individual polymer chains and biomolecular surface[2]

§ Linear or star-like shape[2]

o  Biomolecule-crosslinked polymer nanocapsules[2]

§  Nanocapsules with biomacromolecules centered within polymer shells[2]

II. Clay Nanocomposites

·            First commercial application of the clay nanocomposites formed by in-situ polymerization was used by Toyota Motor Corp in the early 1990s[3]

·            Useful in terms of increasing strength, thermal stability, and penetrating barriers[4]

·            Study investigated the role of the initiator in the in situ polymerization process of clay nanocomposites[4]

o  More favorable nanocomposite product is produced with a more polar monomer and initiator[4]

III. Carbon Nanotubes (CNT)

Figure 2: Depiction of carbon nanotube

(Source: Wikimedia Commons)

-              This figure will help clarify how a carbon nanotube, one of the key nanoparticles of in situ polymerization, actually looks like

·            many real world applications due to remarkable mechanical, thermal and electronic properties (high conductivity, large surface area, excellent thermal stability, etc.) [5]

o  strengthens composites as filler material[5]

o  energy production, conductive properties[6]

·            single walled nanotubes (SWNT) and multi-walled nanotubes (MWNT) [5]

·            In situ polymerization is an important method of preparing polymer grafted nanotubes using carbon nanotubes

o  Advantages

§ Allows polymer macromolecules to attach to CNT walls[5]

§ Resulting composite is miscible with most types of polymers[5]

§ Unlike solution or melt processing, in situ polymerization can prepare insoluble and thermally unstable polymers[5]

§ Can achieve stronger covalent interactions between polymer and CNTs earlier in the process[5]

·            Applications

o  Electrodes made from CNT

§ In situ polymerization has been studied to streamline the construction process of such electrodes[6,7]

·            CNT/PMMA composite electrode[7]

§ In situ polymerization can potentially produce composites of conductive CNTs on a grand scale[6]

·            Cost effective with regards to operation[7]

·            Minimal sample required[7]

·            High sensitivity[7]

·            Many promising environmental and bioanalytical applications[7]

IV. Biopharmaceuticals

·            Proteins, DNAs, and RNAs

o  Potential to treat various disorders and diseases ranging from cancer to infectious diseases[2]

o  Undesirable properties such as poor stability, susceptibility to enzyme degradation, and insufficient capability to penetrate biological barriers[2]

o  In situ polymerization offer a means of overcoming these hindrances and improving the effectiveness of such biopharmaceuticals[2]

o  In Situ Polymerization Methods

§ “Grafting-from” polymerization[2]

§ differs from standard “grafting to” polymerization, which involves straightforward attachment of polymers to biomolecule of choice[2]

§ “grafting from” method is in situ method that takes place on proteins pre-modified with initiators[2]

·            atom transfer radical polymerization (ATRP)[2]

·            reversible addition-fragmentation chain transfer (RAFT)[2]

§ Radical polymerization with crosslinkers[2]  

·            Produces nanogels/nanocapsules via covalent or non-covalent approach[2]

o  Covalent = conjugate acryloyl group to protein followed by in situ freer adical polymerization[2]

o  Non-covalent = entraps protein within nanocapsules[2]

o  Significance

§ Improve stability, bioactivity, and ability to cross biological barriers[2]

V. Urea Formaldehyde (UF) and Melamine Formaldehyde (MF)

·            Emulsification of oil phase in water[8,9]

·            Add water-soluble urea/melamine formaldehyde resin monomers, which are allowed to disperse[8,9]

·            Add acid to lower pH = initiation[8,9]

·            Crosslinking of resins à results in shell of polymer-encapsulated oil droplets[8,9]

Bibliography

1.        Manufacturing Techniques for Polymer Matrix Composites (PMCs) by Suresh G. Advani, Kuang-Ting Hsiao

2.        In situ polymerization on biomacromolecules for nanomedicines

3.        Synthesis and properties of polyimide‐clay hybrid films

4.        Poly(methyl methacrylate) and Polystyrene/Clay Nanocomposites Prepared by in-Situ Polymerization

5.        Small but strong: A review of the mechanical properties of carbon nanotube–polymer composites

6.        In situ polymerization and characterizations of polyaniline on MWCNT powders and aligned MWCNT films

7.        Carbon Nanotube/Poly(methyl methacrylate) (CNT/PMMA) Composite Electrode Fabricated by In Situ Polymerization for Microchip Capillary Electrophoresis

8.        Advances in Thermal Energy Systems by Luis F Cabeza

9.        Advances in the Dyeing and Finishing of Technical Textiles by Mohan L. Gulrajani

10.  Versatile Protein Nanogels Prepared by In Situ Polymerization