June 20,2019
Mandom Corporation
Kyoto University

Mandom and Kyoto University develop a new hair-stylingtechnology that forms moisture-proof bonding inside hairto keep naturally finished hairstyles
Mandom Corporation (Head Office: Osaka City, Japan; President Executive Officer & Director: Motonobu
Nishimura; hereinafter called Mandom) and Kyoto University (Kyoto, Japan; President: Juichi Yamagiwa; joint
researchers: Associate Professor Hikaru Takaya and Assistant Professor Katsuhiro Isozaki; hereinafter called
Kyoto University) have been working together since 2014 to develop hair-styling technology to meet thedemand for naturally finished hairstyles.
In conventional hair-styling approaches, styling ingredients are usually applied or attached onto the outsideof every hair to hold some hairs in bundles or to glue hairs to each other to keep the hairstyle. However, hairwith heavy styling ingredients often looks solid and has a heavy finish, in contrast to the current demand forhair-styling products to simultaneously provide natural finish and hold, which have been incompatible so far.
Against this background, Mandom started research into potential hair-styling ingredients that can act insidehair, assuming that the formation of strong bonds inside each hair could provide a strong holding power underhigh humidity conditions.
As a result, α-ketoglutarate, which has been used in moisturizers, was found to be a potential to achieveboth natural finish and strong hold at the same time through penetration and bond-forming action inside hairs.
This technology enabled us to develop new styling products with which users can keep their desired
hairstyle with a natural finish.
The results of this study will be reported at the 30th International Federation of Societies of CosmeticChemists (IFSCC) Conference held in Milan, Italy, from September 30th to October 2nd, 2019.
1.
Young men’s need for compatibility between natural finish and keeping hairstyle
As described above, conventional hair-styling technology involves the application of hair-styling ingredientssuch as set polymers or wax on the outer surface of hairs, which act to solidify or glue hairs to each other tokeep the hairstyle (Fig. 1). Consequently, while applying a larger volume of hair-styling ingredients to externalhairs provides stronger fixing of hairs together, the finish becomes solid and heavy.

Hair appearance

Hair cross-section

Hair appearance

Hair cross-section

Set polymer
Wax
Figure 1: Conventional hair-styling technology (acting on hair externally)
While this solid, heavy finish has been favorably accepted by many consumers, the number preferring-1-

naturally finished hairstyles has been on the rise lately, particularly among young men. This trend has createddemand for new styling products that can preserve hairstyles with a natural finish (Fig. 2).
Existing externally acting hair-styling technology has been inadequate for natural finishes because thestronger the holding power, the larger the volume of hair-styling ingredients required for coating the hair. The
development of new technology to satisfy the demand for hold with a natural finish is therefore required.
Natural finish
・Current hair trend
・Light-looking finish like natural hair→Comparable level of shine to natural hair

Heavy finish
・Conventional hair trend
・Heavy finish, hair appears hardened→Glossy as if hair surface is coatedFigure 2: Two major types of finish with hair-styling products
2.
Search for hair-styling ingredients that penetrate into and act on the inside of hair
Humidity is the main cause of the loss of hairstyle shape. Hair is composed of proteins, most of which formhydrogen bonds to provide each hair a shape. These hydrogen bonds are highly vulnerable to water; once
exposed to moisture, the hydrogen bonds are cleaved , changing the hair shape. This is one of the reasons
humidity can disarrange hairstyles (Fig. 3).

Humidity

Hairstyle loses its shape because
moisture breaks hydrogen bonds,
changing the shape of each hair.

: Hydrogen bond: Protein in hair

Figure 3: Schematic of hair proteins held together with hydrogen bonds
Mandom hypothesized that resistance to moisture could be improved by infusing active ingredients into hairthrough formation of ionic bonds between hair proteins. Ionic bonds provide stronger association thanhydrogen bonds (Fig. 4).
Humidity
Ionic bonds are more resistant
tohumidity

thanhydrogenbonds.

: Hydrogen bond: Ionic bond

: Protein in hair

Figure 4: Schematic of hair proteins held together with ionic bonds
Proteins in hair have positively charged sites. If they interact with a molecule with negatively charged acidgroups at each end, bridges between individual hair proteins are expected to form through ionic bonds (Fig. 5).

-2--NH4

OOC-R-COO

H4N-(Amino group)(Dibasic acid)(Amino group)

Dibasic acids caneasily form ionic bonds
with amino groups
through the charged
sites at both ends

Figure 5: Schematic of ionic bonds between dibasic acid and hair proteins
After investigating a series of dibasic acids, Mandom found that α-ketoglutarate, which is used as amoisturizing ingredient, could penetrate into hair efficiently and improve moisture resistance. It was alsoconfirmed that hair treated with α-ketoglutarate had a similar finish to native hair. We concluded thatapplication of α-ketoglutarate could provide a natural finish and hairstyle holding power in one hair-styling
product.
Permeability:
Hair immersed in an α-ketoglutarate solution was cut and the distribution of α-ketoglutarate on the cut
surface was analyzed by Raman spectroscopy. The results showed α-ketoglutarate permeating into the core of
the hair fiber (Fig. 6).
α-Ketoglutarate
concentrationHigh

Test method:
After hair had been
immersed inα-ketoglutarate solution

Lowfor 2 hours, the cut
surface was mapped by
Raman spectroscopy at

Untreated hair

α-Ketoglutarate-treatedthe specifichair

α-ketoglutarate peak of1739 cm-1

Figure 6: Permeation of α-ketoglutarate into hair
Bonding with hair protein:
To confirm whether the penetrated α-ketoglutarate binds to hair-protein, small-angle X-ray scattering(SAXS), which allows micron-scale structural analysis, was performed at Kyoto University.
SAXS provides a X-ray scattering pattern, in which sequential length and structural regularity of hairproteins are identified by the angle and intensity of scatterings. Higher scattering intensity suggests that thehair has a more regular shape and structure (Fig. 7).

-3-Intensity of scattered
X-rays: HighScattering intensity

In graph

X-raysScattering angle 2θ

When hair proteins are regularly arranged

Scattering intensity

Intensity ofscattered X-rays:
LIn graph

HairX-rays

Scattering angle 2θ

When hair proteins are not regularly arranged

SAXS result
Figure 7: Schematic of SAXS study

There was a remarkable difference in SAXS intensity at the region of matrix protein between hair treatedwith α-ketoglutarate and with purified water (Fig. 8). The matrix protein structure was broken in normal hair
when it was stored under humid conditions, whereas the matrix protein structure of hair soaked in
α-ketoglutarate formed a regular arrangement that was maintained irrespective of humidity.
Matrix protein-derived area(2θ = 1.7-1.9)
Treated with α-ketoglutarate+ Storage under high humidity
Scattering

Treated with purified water+ Storage under high humidity

intensity[cps]

Test method: After hair had been immersed in either 0.5%
α-ketoglutarate solution or purified water for 2 hours, it wasdried and placed in the SAXS sample cell. X-ray wasirradiated to the hair placed in the closed cell filled with 40 °C

Scattering angle 2θ [deg]water.

Figure 8: SAXS patterns of treated hairs after storage under high humidity
This is evidence of the effect of α-ketoglutarate on hair matrix protein. α-Ketoglutarate binded to hair protein
and formed a robust, regularly arranged structure that was not affected by humidity (Fig. 9).

-4-Matrix protein
Microfibril(Protein filling in the gaps between microfibrils)
MatrixMacrofibril
MedullaCortex cellCuticle

ImageStorage under high humidity

Matrix protein
Hydrogen bonding
α-Ketoglutarate bonding

Hair treated with α-ketoglutarate
 Structure NOT altered byhumidity

Hair treated with purified water Structure altered by humidity

Figure 9: Regular structure of matrix protein under high humidity(Based on the results in Fig. 8)
Moisture resistance:
A bundle of hair treated with α-ketoglutarate was curled around a rod, dried, and left for 2 hours underhigh-humidity conditions of 25 °C and 80% relative humidity (RH) to measure the endurance of the hair curls.
When hair absorbs moisture, internal hydrogen bonds are usually cleaved and it uncurls. In this test, hairtreated with α-ketoglutarate was compared to hair treated with other dibasic acid and purified water to identify
the extent to which α-ketoglutarate could maximize the curl retention under high humidity.
The results showed that α-ketoglutarate treatment had higher curl retention with improved holding power
than water and glutarate treatment (Fig. 10).

Curl retention [%]= (*A after 2 hours/A baseline) ×100

Tested hair bundles 2 hours aftertreatment(a) Purified water (b) Glutarate (c) α-Ketoglutarate
Test method:30-cm long hair bundles were immersed in 0.5% aqueous solutions containing each treatment ingredient (or pure water
for untreated hair) for 2 hours, then curled around a rod and dried for a day at a room temperature of 25 °C and 60% RH.
After removing the rods, the hair bundles were left for 2 hours at a room temperature of 25 °C and 80% RH, and hairlength was measured over time.
* A＝B: Length of the hair bundle before treatment (cm) - C: Length of the hair bundle at different measurement time
points (cm)Figure 10: Curl retention results of curled hair stored under high humidity
Natural finish:α-Ketoglutarate was applied to hair bundles to evaluate whether α-ketoglutarate could provide a natural
texture by observation of shine on the dry hair surface. For comparators, other hair bundles treated with-5-

purified water, set polymer (Mandom hair gel as a traditional hair-styling ingredient), and wax (Mandom hairwax) were also prepared.
Hair bundles treated with the set polymer and wax were glossier than that treated with purified water, while
the hair bundle treated with α-ketoglutarate had a similar amount of gloss to that treated with purified water(natural finish) (Fig. 11).
Purified water

0.5% α-ketoglutarate

Set polymer (Mandom hair gel)Wax (Mandom hair wax)

Appearance

Test method:
Hair appearance was observed after 0.4 g of each sample was applied and soaked into the 20-cm longflat hair bundles and naturally air-dried.

Figure 11: Evaluation of shine in hair bundles coated with samples

In summary, Mandom succeeded in developing a hair-styling technology with α-ketoglutarate that can takeeffect from the inside of hair fibers and ensure the hairstyle could be preserved all day under humid conditions.
Mandom intends to apply this technology in our hair-styling products to provide both natural finish andholding power.

-6-Contact＜About the research contents＞
Assistant Professor Katsuhiro Isozaki
International Research Center for Elements Science, Institute for Chemical Research Kyoto University
Yoshida Honmachi Sakyo, Kyoto 606-8501 Japan
Tel: +81-774-38-3182
E-mail: kisozaki@scl.kyoto-u.ac.jp
Shun Urabe
Mandom Corporation Technical Development Center
5-12, Juniken-cho, Chuo-ku, Osaka 540-8530, Japan
E-mail: pess@mandom.com＜About this news release＞
Kyoto University Public Relations Division Global Communications Office
36 Yoshida Honmachi Sakyo, Kyoto 606-8501 Japan
Tel: +81-75-753-5729 Fax: +81-75-753-2094
E-mail: comms@mail2.adm.kyoto-u.ac.jp
Mandom Corporation Public Relations Div.
5-12, Juniken-cho, Chuo-ku, Osaka 540-8530, Japan
E-mail: press@mandom.com-7-