This invention relates to siloxane-based polymers (polysiloxanes) with different architectures and molecular weights that contain units that are capable of forming strong H-bridges with each other leading to reversible physical interactions between different polymer chains in bulk and in solution. The supramolecular H-bridge interactions are specific as they exist between self-complementary units containing 4 hydrogen bonds in a row (i.e. 4H-units), and the action of these 4H-units results in superior material characteristics. For details on the 4H-unit, see Sijbesma et al. WO 98/14505; Science, 278, 1601.
Although several telechelic polymers have been modified with 4H-units before (Folmer, B. J. B. et al., Adv. Mater. 2000, Vol. 12, 874), only one example of a low molecular weight telechelic polysiloxane modified with 4H-units has been described previously in patent WO 98/14505; (later published in Hirschberg et al., Macromolecules 1999, Vol. 32, 2696). Major drawback of the polysiloxane polymer described in this patent is the elaborate procedure to couple the 4H-unit to the polymer in which a protection/deprotection procedure is necessary. Moreover, the resulting polymer contains only two 4H-units on both ends and has a limited molecular weight.
This invention is further related to the use of polysiloxanes functionalized with 4H-units as gelling agents for silicone fluids (for example, volatile or non-volatile silicone liquids). The resulting gels are clear and contain small amounts of gelling agent; their physical characteristics can be fine-tuned by selecting the right 4H-unit modified polysiloxane or by combining a set of such polysiloxanes. Moreover, the prepared gels can be used in personal care applications, for example as carriers for cosmetic or dermatological active ingredients in order to obtain cosmetic or dermatological active compositions. Particular embodiments of the present invention are skin-care compositions such as deodorant and antiperspirant compositions, sun protection compositions and hair-care compositions.
Because gels based on volatile silicones (cyclomethicones) reduce tackiness and stickiness of cosmetic or dermatological formulations, there has been an increasing need for cosmetic or dermatological compositions with high cyclomethicone content. In U.S. Pat. No. 5,500,209 this has been achieved by using polyamides as gelling agent, however only limited amounts of cyclomethicones can be added because of the immiscibility with the polyamide and the high crystallinity of the polyamide.
In order to improve the miscibility with silicone fluids, polyamides containing polysiloxane blocks have been prepared, as described in U.S. Pat. No. 5,874,069, and U.S. Pat. No. 6,353,076B1. Drawbacks of these inventions are the poor gelling characteristics compared to the gellants disclosed here, because of the relatively weak interactions between different polyamides. As a consequence, high molecular weight polymers have to be used to obtain stable gels, the amount of gelling agent has to be high, and non-silicone viscosity builders have to be added.
In U.S. Pat. No. 5,919,441 main-chain siloxane urea polymers are used containing polysiloxane-segments and polar segments with urea, urethane, amide and thiourea groups or combinations of these groups. Drawbacks of this invention are the high molecular weights of the used polymers, hampering good processability of the material, and the presence of a relatively high amount of non-siloxane, cyclomethicone immiscible groups, thereby reducing the amount of cyclomethicone that can be thickened by the gelling agent. Moreover, a major drawback of this invention is the relative weakness of the secondary interactions between different polysiloxanes, as this requires high amounts of thickener to obtain stable gels and additional viscosity builders in the cosmetic applications.
This invention describes the unprecedented synthesis of polysiloxanes containing one or more 4H-units capable of forming strong, but reversible physical interactions with each other. Due to the presence of the 4H-units the polysiloxanes display unique new material properties in bulk and in solution. In a particular embodiment of this invention, the effective gelling behavior of these modified polysiloxanes is used to thicken volatile silicone solvents, creating transparent gels with low or very low thickener content and excellent material properties. The resulting thickened volatile silicones are ideal carriers for cosmetic or dermatological active ingredients and therefore have several cosmetic or dermatological applications.