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Self-organizing cyclolinear organosilicon polymers in bulk and on the surface of water.

Makarova NN, Astapova TV, Buzin AI, Polishchuk AP, Chizhova NV, Petrova IM - Int J Mol Sci (2013)

Bottom Line: It was shown that on introduction of CH2 groups into the methylcyclohexasiloxane unit, the polymer retains the ability to self-organize with formation of a mesomorphic state in a wide temperature range, while on introduction of (CH2)2 fragments in a cyclotetrasiloxane unit or in a bridge connecting two methylcyclotetra(hexa)siloxane units it does not.It was revealed that all polymers form monomolecular films at the air/water interface, excluding those having longer hydrophobic fragment than hydrophilic ones.The ability to form multilayers depends on the surroundings of Si atom in the bridge between the cycles.

View Article: PubMed Central - PubMed

Affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova str., Moscow 119991, Russian Federation. buzin@cc.nifhi.ac.ru.

ABSTRACT
Cyclolinear organocarbosiloxane polymers with varying content and location of (CH2)n groups in the monomer unit were synthesized by reactions of heterofunctional polycondensation and polyaddition of difunctional organocyclosiloxanes and organocyclocarbosiloxanes. Their bulk properties were studied by differential scanning calorimetry and X-ray structural analysis. It was shown that on introduction of CH2 groups into the methylcyclohexasiloxane unit, the polymer retains the ability to self-organize with formation of a mesomorphic state in a wide temperature range, while on introduction of (CH2)2 fragments in a cyclotetrasiloxane unit or in a bridge connecting two methylcyclotetra(hexa)siloxane units it does not. Comparison of the X-ray data of dihydroxy derivatives of decamethylcyclohexasiloxane and decamethyl-5-carbocyclohexasiloxane with packing of cyclolinear organosilicon polymers in bulk shows that the polymer inherits the layered type of crystalline structure typical for monomers. Langmuir films of cyclolinear polymethylcarbosiloxanes with different design of monomer units were studied as well. It was revealed that all polymers form monomolecular films at the air/water interface, excluding those having longer hydrophobic fragment than hydrophilic ones. The ability to form multilayers depends on the surroundings of Si atom in the bridge between the cycles.

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π-A isotherms of CL POS II-Me and CL PMCS IV–VI on water at 20 °C.
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f8-ijms-14-18215: π-A isotherms of CL POS II-Me and CL PMCS IV–VI on water at 20 °C.

Mentions: Figure 8 presents the π-A isotherms of methyl substituted Polymers II and IV–VI with different structures of monomer units. Replacement of an oxygen atom by a hydrocarbon fragment (IV-Me and VI-Me) causes no changes in the surface area occupied by the monolayer on the surface of water; at the same time, the surface pressure decreases by 2.5–3 mN m−1. Thus, macromolecules on the surface are arranged similarly, and the π value decreases because the methylene units are surface inactive. On the other hand, the π-A isotherms of Polymers IV and VI have fundamentally different shapes. Replacement of the oxygen bridge in Polymer IV-Me by the hydrophobic ethylene group leads to the loss of the multilayer character of monolayer collapse, whereas replacement of the ring oxygen atom by a methylene unit in Polymer VI causes no changes in it. The character of the surface pressure isotherm of Copolymer V-Me with ethylene bridges between alternating cyclohexa- and cyclooctasiloxane moieties is similar to the case of CL PMCS IV-Me. Thus, it is the inter-ring oxygen atom that determines the character of intermolecular packing of polymer chains in the cyclohexasiloxane monolayers. Replacement of this oxygen atom by the ethylene bridge causes suppression of the mesophase in the bulk of the sample as well as the loss of the multilayer character of the π-A isotherm on the water surface for Polymers IV-Me and V-Me.


Self-organizing cyclolinear organosilicon polymers in bulk and on the surface of water.

Makarova NN, Astapova TV, Buzin AI, Polishchuk AP, Chizhova NV, Petrova IM - Int J Mol Sci (2013)

π-A isotherms of CL POS II-Me and CL PMCS IV–VI on water at 20 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3794777&req=5

f8-ijms-14-18215: π-A isotherms of CL POS II-Me and CL PMCS IV–VI on water at 20 °C.
Mentions: Figure 8 presents the π-A isotherms of methyl substituted Polymers II and IV–VI with different structures of monomer units. Replacement of an oxygen atom by a hydrocarbon fragment (IV-Me and VI-Me) causes no changes in the surface area occupied by the monolayer on the surface of water; at the same time, the surface pressure decreases by 2.5–3 mN m−1. Thus, macromolecules on the surface are arranged similarly, and the π value decreases because the methylene units are surface inactive. On the other hand, the π-A isotherms of Polymers IV and VI have fundamentally different shapes. Replacement of the oxygen bridge in Polymer IV-Me by the hydrophobic ethylene group leads to the loss of the multilayer character of monolayer collapse, whereas replacement of the ring oxygen atom by a methylene unit in Polymer VI causes no changes in it. The character of the surface pressure isotherm of Copolymer V-Me with ethylene bridges between alternating cyclohexa- and cyclooctasiloxane moieties is similar to the case of CL PMCS IV-Me. Thus, it is the inter-ring oxygen atom that determines the character of intermolecular packing of polymer chains in the cyclohexasiloxane monolayers. Replacement of this oxygen atom by the ethylene bridge causes suppression of the mesophase in the bulk of the sample as well as the loss of the multilayer character of the π-A isotherm on the water surface for Polymers IV-Me and V-Me.

Bottom Line: It was shown that on introduction of CH2 groups into the methylcyclohexasiloxane unit, the polymer retains the ability to self-organize with formation of a mesomorphic state in a wide temperature range, while on introduction of (CH2)2 fragments in a cyclotetrasiloxane unit or in a bridge connecting two methylcyclotetra(hexa)siloxane units it does not.It was revealed that all polymers form monomolecular films at the air/water interface, excluding those having longer hydrophobic fragment than hydrophilic ones.The ability to form multilayers depends on the surroundings of Si atom in the bridge between the cycles.

View Article: PubMed Central - PubMed

Affiliation: Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova str., Moscow 119991, Russian Federation. buzin@cc.nifhi.ac.ru.

ABSTRACT
Cyclolinear organocarbosiloxane polymers with varying content and location of (CH2)n groups in the monomer unit were synthesized by reactions of heterofunctional polycondensation and polyaddition of difunctional organocyclosiloxanes and organocyclocarbosiloxanes. Their bulk properties were studied by differential scanning calorimetry and X-ray structural analysis. It was shown that on introduction of CH2 groups into the methylcyclohexasiloxane unit, the polymer retains the ability to self-organize with formation of a mesomorphic state in a wide temperature range, while on introduction of (CH2)2 fragments in a cyclotetrasiloxane unit or in a bridge connecting two methylcyclotetra(hexa)siloxane units it does not. Comparison of the X-ray data of dihydroxy derivatives of decamethylcyclohexasiloxane and decamethyl-5-carbocyclohexasiloxane with packing of cyclolinear organosilicon polymers in bulk shows that the polymer inherits the layered type of crystalline structure typical for monomers. Langmuir films of cyclolinear polymethylcarbosiloxanes with different design of monomer units were studied as well. It was revealed that all polymers form monomolecular films at the air/water interface, excluding those having longer hydrophobic fragment than hydrophilic ones. The ability to form multilayers depends on the surroundings of Si atom in the bridge between the cycles.

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