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Structure Function Relationships of Dimethicone Copolyol
  • By;
  • Anthony J. O'Lenick
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Dimethicone Copolyol, DMC
  • DMC surfactants and their derivatives are an important and growing class of surfactants.
  • They are used in a diverse area of applications due to their ability to provide maximum surface active properties in a cost-effective manner.
  • Despite their growing use, studies regarding the basic understanding of the chemistry and the effect of structure on surfactant properties remain limited.
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DMC Surfactants General Structure
  •                        CH3       CH3        CH3        CH3
  •                                       |          |            |             |
  •                              CH3—Si— (O-Si-)a—(O-Si )b—O—Si—CH3
  •                                       |          |            |             |
  •                                       CH3     CH3       (CH2)3       CH3
  •                                                                |
  •                                                                O-(CH2CH2O)x-yH
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DMC Surfactant Derivatives
General Structure
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General Reaction Scheme for
the Synthesis of DMC
  •                          CH3             CH3               CH3                   CH3
  •                                                         |                 |                   |                 |
  •    CH3 --- Si ---(-O --- Si ---)a--- (-O--Si ---)b—O—Si—CH3
  •                                                          |               |                     |               |
  •                                                          CH3           H                     CH3           CH3


  • +  “a” moles of CH2=CH-CH2-O-(CH2CH2O)x-H
  •                                                                                        catalyst       D


  •                                                                  CH3            CH3               CH3                       CH3
  •                                                                    |               |                   |                 |
      •                                        CH3 --- Si ---(-O --- Si ---)a--- (-O--Si ---)b—O—Si—CH3
  •                                                                    |               |                    |                |
  •                                                                    CH3           (CH2)3            CH3             CH3
  •                                                                                      |
  •                                                                                     O- (CH2CH2O)x-H
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DMC Nomenclature - “shorthand”
  •          CH3                                                         CH3
  •                 |                                          |
  • “M”      -O-Si-CH3                  “D”       -O-Si-O-
  •                 |                                          |
  •                 CH3                                                          CH3



  •                 |                                          |
  •                 O                                                             O
  •                 |                                          |
  • “T”      -O-Si-CH3                  “Q”       -O-Si-O-
  •                 |                                          |
  •                 O                                         O
  •                 |                                           |
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DMC Nomenclature - Organofunctional
  •          CH3
  •                  |
  • “M*”     -O-Si- CH3
  •                  |
  •                 R          where R = functional group


  • For example, the structure for MD2D3*M is:
  •       CH3     CH3         CH3      CH3
  •       |        |         |        |
  • CH3-Si-(O-Si)2-(O-Si)3-O-Si-CH3
  •       |       |          |        |
  •      CH3    CH3      R        CH3
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Properties Evaluated
    • Solubility
    • Cloud point
    • Surface tension/cmc
    • Spreading (in a polyester surface)
    • Foaming (ASTM D 1173)
    • Emulsification
    • Draves wetting (ASTM D 2281)
    • Draize primary ocular irritation (via independent lab)
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 DMC Structures Synthesized
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Solubility at 1%w (24oC)
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Cloud Point
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Surface Tension and CMC
(24°C, DI water)
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Spreading
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Spreading
  • The isomers studied spread slightly better than water but cannot be considered superspreaders.


  • These materials are too hydrophilic and thus do not contain the needed subphases present that provide the necessary surfactant concentration gradient in the droplet spreading front that drives the spreading.


  • SL/S = gSA - (gSL + gLA)    where A=air, L=liquid, S=substrate
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DMC Foaming at 1% w (ASTM D1173)
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DMC Emulsification Ability
(5% DMC/47.5% Water/47.5% Oil, mixed 5 min. at high shear)
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Wetting of DMC’s
  • There is a strong relationship between molecular weight and wetting.  The lower molecular weight materials have faster wetting times.


  • The smaller molecule allows for more efficient packing efficiency and dynamics.  The materials with lower molecular weight were extremely effective at the higher concentration.
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Draize Primary Ocular Irritation
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Summary
  • Solubility in polar media seems to relate to the length of the polyoxyethylene group.


  • Products with higher molecular weight had better dispersibility in nonpolar oils.


  • The cloud point is related to the length of the polyoxyethylene group in the molecule and was rather independent of the silicone portion of the molecule.


  • The molecules studied spread slightly better than water but cannot be considered superspreaders.
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Summary

  • The lower molecular weight materials have faster wetting times.


  • The higher the molecular weight the lower the ocular irritation.


  • The proper selection of a dimethicone copolyol can result in a product that has a desirable combination of properties.


  • The properties, when correlated to the irritation data, allow for selection of cost-effective materials that are both effective and possess low irritation potential.
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