Home Cosmetic Science Talk Formulating Advanced Questions Surfactant Chain lengths?

  • letsalcido

    June 24, 2020 at 8:08 am

    Two examples:

    Decyl Glucoside (C10)*
    Caprylyl/Capryl Glucoside (C8-C10)

    * double check with the manufacturer because I found at least two sellers claiming their product has C8-C16 and another C8-C10. But strictly from the name it should be C10 only.

     Is there a specific reason why you would like to avoid those chain lengths?

  • Pharma

    June 24, 2020 at 11:49 am
    Decyl glucoside is often a mixture with a higher % of decanol (still likely less than 50%) whereas caprylyl/capryl glucoside is rich in octanol and decanol but as well doesn’t contain just these two.
    The chains of emulsifiers are most commonly fatty acids whereas many common surfactants contain fatty alcohols instead. These are usually derived from fatty acids (anionics such as alkyl sulfates, alkylether sulfates, sulfoacetates, most synthetic nonionics, and glucosides). Performance and feel are +/- identical between ester and ether/acetal groups. Quaternary ammonium soaps usually don’t contain either but are made out of ‘pure’ hydrocarbon chains linked to the ammonium nitrogen via C-N bonds. Also, alkyl- and alkylbenzenesulfonates don’t contain fatty acids/alcohols but ‘pure’ hydrocarbons linked in this case to the sulphur atom via C-S bonds.
    Is there any reason why you don’t want anything fatty acid derived? And what’s the reason behind the C12-C24? Why not C10? Nearly all commercial surfactants have chain lengths between C10 and ~C24 because shorter than C10 turns them too hydrophilic to function as surfactant whereas very long chains would make them very powerful surfactants weren’t it for the fact that these are usually no longer soluble in either phase and have too high melting points (extended surfactants are an exception but these are not used in cosmetics).
    Honestly, to me you sound like haveing no real clue of surfactants… (no offence!)
  • letsalcido

    June 24, 2020 at 4:30 pm

    @Pharma yes what you say aligns with most of the manufacturer’s notes I’ve seen. But I had come across at least one that claimed only decanol as the starting point https://www.ulprospector.com/en/na/PersonalCare/Detail/5303/601422/Endinol-MILD-DG-1050?st=1&sl=92034918&crit=RGVjeWwgR2x1Y29zaWRl&ss=2
    So it seems your mileage may vary, but given that OP likely does not need analytical grade high purity surfactants, the two I mentioned fit the bill keeping in mind there will be other chain lengths in there. Good to point out they’re not pure as I implied though.

    Regarding your other observations about the fatty acids/fatty alcohols. While I was gonna comment something similar, don’t most cosmetic surfactants begin as fatty acids from Coconut/Palm and other vegetable sources nowadays? You even mentioned most surfactants come from fatty alcohols made from fatty acids. I think OP is not a chemist and they just tried to express something the way they could, and I don’t think it was inadequate. Only weird thing is trying to avoid those chain lengths… curious to hear the reasoning behind it.

    Good detailed explanation nonetheless! 
  • Pharma

    June 24, 2020 at 7:56 pm
    Ups… did translate/interpret OP’s phrase the wrong way… she/he is looking for something outside the C12-C24 range. And that more or less leaves her/him with C10/decyl or such based on octacosanol or triacontanol such as octacontyl sulfate or triacontyl phosphate (which, to my knowledge, do only exist in patents and as research chemicals). Or rhamnolipids and trehalolipids might work (they’re for example based on two C8 and are often not standard fatty acids but derivatives) ;) .
    Good reading: Renewable Surfactants for Biochemical Applications and Nanotechnology by Sarah Le Guenic et al.

  • Choycer

    June 25, 2020 at 3:35 pm

    @Pharma @letsalcido Thanks guys so much for taking the time to respond. I am not a chemist although I have been pondering the idea of going back to school to get my degree. Either way I am passionate about skin care and wanted to formulate a face wash without fatty acids including c12- c24 because I read that it can feed Malassezia (Pityrosporum) folliculitis through a blog called http://www.simpleskincarescience.com and it’s related articles. With my own research I have read that Decyl glucoside contains c8-c16. I believe that my question may have been too open for interpretation because I did not explain my reasoning, apologies. I’ve already had Capryl Glucoside in mind, but was wondering if there were any others. Thanks again for the recommendations!

  • belassi

    June 25, 2020 at 7:19 pm

    You’ve got completely the wrong idea, I think. Surfactants are not fatty acids. Oils are fatty acids.

  • Bill_Toge

    June 25, 2020 at 10:00 pm
    oleic acid can aggravate Malassezia growth; surfactants based on C12-24 acids, saturated or unsaturated, generally don’t
    also, outside C12-24 they’re not effective surfactants; they’re either too hydrophilic (< C12) or too hydrophobic (> C24) to be active at the oil/water interface

  • Choycer

    June 26, 2020 at 3:54 pm

    @Belassi @Bill_Toge hi guys! These are what I’m trying to avoid (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1198797/pdf/biochemj00724-0062.pdf

    • Undecylenic Acid (C11)
    • Lauric / Dodecanoic (C12)
    • Tridecylic (C13)
    • Myristic / Tetradecanoic (C14)
    • Pentadecanoic (C15)
    • Palmitic / Hexadecanoic (C16)
    • Palmitoleic / Hexadecenoic (C16:1)
    • Margaric (C17)
    • Stearic / Octadecanoic (C18)
    • Oleic / Octadecenoic (C18:1)
    • Linoleic (C18:2)
    • α-Linolenic (C18:3)
    • Nonadecylic (C19)
    • Arachidic / Eicosanoic (C20)
    • Heneicosylic (C21)
    • Behenic / Docosanoic (C22)
    • Tricosylic (C23)
    • Lignoceric / Tetracosanoic (C24)
  • letsalcido

    June 26, 2020 at 7:53 pm

    @Choycer strictly speaking, like Belassi said, surfactants are not fatty acids. They’ve gone through chemical reactions that change their identity and behavior completely! Cleansers (if formulated well) will rinse off completely for the most part, they are also denaturing to biological membranes (bacteria and virus) and proteins (virus) to a certain extent, some are even used as disinfectants, like in the case of Quaternary Ammonium Compounds, most of which would contain at least some of the carbon chains you’re trying to avoid.

    Again, surfactants are NOT fatty acids. A covalently bound molecule is NOT the same as a mixture of molecules. I can mix ammonium sulfate and lauric acid and it will not be the same as Ammonium Lauryl Sulfate (ALS). One is a mixture of compounds, the other is a completely new compound.

    I think you should listen to Bill and Belassi, and revaluate what you are considering here. 

    As a side note: if you are going by what companies and DIYers say (olive oil soap is moisturizing because of the linoleic acid/Omegas, etc. just don’t do it. It’s all unscientific nonsense. Once reacted, the oils used for making a soap or detergent are no longer oils and their original benefits are for the most part gone).

  • Pharma

    June 26, 2020 at 8:57 pm
    If you want to play on the safe side, go with stuff bacteria can’t digest, not just short fatty acid chains (which they could but don’t like because of membrane destabilising effects) and long fatty acid chains (which they can’t easily eat because of very poor water solubility). I’m thinking silicone and paraffin oils and silicone/PEG/PPG surfactants. Problem solved.
    Although a surfactant is no longer a fatty acid (except for fatty acid salts), they may be metabolised (like triglycerides) by bacteria and there is reason to suspect that certain fatty acids such as oleic acid may favour growth of certain bacteria even if covalently linked. However, simply demonising 99.9% of all biologically relevant fatty acids is utterly stupid because your skin is made of a good portion of exactly that.
    On the other hand, you would have to ban all triglycerides and most other oils from your creams and, as said, be left with silicones and hydrocarbons.
  • Choycer

    June 27, 2020 at 7:38 am

    @Pharma @letsalcido thanks so much guys for your feedback, really appreciate it! 

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