Disclosed are compositions and methods for treating and modifying surfaces and for enhancing delivery of active agents to surfaces treated with the compositions, which comprise siloxane polymers functionalized with pendant moieties comprising anionic groups, specifically carboxylic acid groups. When applied to a suitable surface, the present composition comprising the carboxy functionalized siloxane polymers forms a substantially hydrophobic coating on the treated surface. These polymers effectively deposit on surfaces that have cationic sites, which are capable of forming bonds or linkages with the anionic groups of the polymer. The treated surface becomes hydrophobic due to the deposition of the carboxy functionalized siloxane polymer, which then imparts a variety of end use benefits to that surface such as ease of cleaning, stain removal and prevention, whitening, etc. The carboxy functionalized siloxane polymer further acts as a carrier to deposit active agents onto the surface and to improve retention and efficacy of said actives on the treated surface. The present compositions are useful in a variety of applications including oral care, hair and skin care, personal care, cosmetics, and fabric and hard surface cleaning and conditioning. Examples are oral compositions for use in cleaning and whitening of natural teeth and dental prosthesis; for preventing, reducing or removing plaque, calculus and surface deposited stains on teeth; and for providing shine, smoothness and positive feel benefits to teeth, the compositions comprising at least about 0.1% by weight of a dicarboxy functionalized siloxane polymer in a formulation that effectively deposits the polymer to teeth and other oral surfaces.