Mechanical Properties of Block Poly(propylene carbonate-cyclohexyl carbonate) Investigated by Nanoindentation and DMA Methodologies Shaoyun Chen, Min Xiao, Shuanjin Wang, Dongmei Han, Yuezhong Meng The Key Laboratory of Low-Carbon Chemistry and Energy Conservation of Guangdong Province/State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, People’s Republic of China Correspondence to: M. Xiao (E-mail: stsxm@mail.sysu.edu.cn) or Y. Meng (E-mail: mengyzh@mail.sysu.edu.cn) ABSTRACT: To extend the practical application of poly(propylene carbonate) (PPC), the chemical methods were used to improve its mechanical properties. In this connection, random copolymer poly(propylene-cyclohexyl carbonate) (PPCHC) and di-block copoly- mers poly(propylene carbonate-cyclohexyl carbonate) (PPC-PCHC) were synthesized. Dynamic mechanical analysis (DMA), nano- indentation and nanoscratch test were applied to evaluate their mechanical properties. The storage’s modulus, Young’s modulus (E) and hardness (H) obtained from DMA and nanoindentation tests showed that the introduction of the third monomer cyclohexene oxide (CHO) can greatly improve the mechanical properties of PPC, and that the block copolymer PPC-PCHC hand better mechani- cal properties than the random copolymer PPCHC. The annealing treated PPC-PCHCs exhibited deteriorated mechanical properties as compared with untreated PPC-PCHC. From the results of scratch tests, the plastic deformation of PPC-PCHC was smaller than those of PPC and PPCHC. Meanwhile, the plastic deformations of the heat-treated PPC-PCHCs were smaller than the untreated PPC-PCHC because of the possible rearrangement of the molecular chains of PPC-PCHC. The scratch hardness (H s ) of the block copolymer PPC-PCHC is larger than random polymer PPCHC and PPC, but lower than the values of heat-treated samples indicating that the surfaces’ hardness of block polymers increase after heat treatment. These different measurement methodologies provide a more precise assessment and understanding for the synthesized block polymers. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 1979–1986, 2013 KEYWORDS: biosynthesis of polymers; mechanical properties; polycarbonates; structure; property relations Received 7 March 2012; accepted 22 July 2012; published online 9 August 2012 DOI: 10.1002/app.38384 INTRODUCTION Biopolymers are increasingly attractive because of their environ- mental issues. Nevertheless, their relatively poor mechanical properties limit their practical applications. In this sense, the assessment of their mechanical behaviors is practically necessary and important. Many new methodologies have been used for this purpose. For example, the scratch test, as a simplification of the complex abrasion process has been used for identifying the main parameters in the wear resistance of material surfaces. 1 During a scratch process, the viscoelastic and viscoplastic behav- iors have been related to dynamic mechanical properties. The distinction between ductile and brittle behavior in scratch pro- cess leads to the definition of some specific tests and para- meters. Ductile deformation during a scratch is often evaluated through the contact pressure, the residual depth of the groove, and the height of the pile-up. 2–7 The microindentation hardness technique has had widespread application in polymer research. 8 The technique has been increasingly used in the characterization of homopolymers, polymer blends, and copolymers. One attractive feature of this technique is its ability for the micromechanical characterization of the polymeric materials. The influence of different molecular parameters (molecular weight, branching degree etc.) on the crystalline morphology in semicrystalline polymers and the microphase separated morphology in block copolymers has been examined in preceding studies using the technique. 9 Young’s modulus and hardness analyzing by nanoindentation permit a direct visualization of the morphology and its influ- ence on the micromechanical deformation processes under the action of an applied load. The micromechanical properties of different amorphous, 9 rubber-toughened, 10 particle-filled poly- mers, 11 and block copolymers 12 can be characterized in detail with help of these techniques. As we all known, carbon dioxide is currently regarded as a major greenhouse gas. 13–16 The utilization of CO 2 became a hot topic of intensive study for the sake of environmental concerns V C 2012 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP J. APPL. POLYM. SCI. 2013, DOI: 10.1002/APP.38384 1979