1,1,1,5,5,5-Hexaethoxy-3,3-dimethyltrisiloxane (QDQ), consisting of di- (D) and quadra-functional (Q) siloxane units, and its polymer (pQDQ) were synthesized. As the comparison, co-hydrolysis of diethoxy(dimethyl)silane (DEDMS) and two equivalents of tetraethoxysilane (TEOS) yielded a copolymer of DEDMS and TEOS (pDEDMS1-TEOS2). The polymer structure and film properties using two types of polymers with an average molecular weight of approximately 10,000 were investigated. The polymer structure was investigated using 29Si NMR and MS. The two films were characterized by thermogravimetric and differential thermal analyses, ultraviolet and visible spectroscopy, and tensile strength and swelling tests. The films from pQDQ and pDEDMS1-TEOS2 exhibited similar chemical structures and physical properties, except for the tensile strength test. The pQDQ film exhibited higher Young’s modulus and breaking stress (455 and 3.7 MPa, respectively) than those of the pDEDMS1-TEOS2 film (55 and 1.1 MPa, respectively), suggesting that the arrangement of the D and Q units affects the mechanical strength of the gel film. Consequently, the mechanical properties of polysiloxane-based materials can be controlled by modifying the sequence of siloxane units. [Figure not available: see fulltext.]