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The morphology of the polymer nanoparticles was analyzed via a scanning electron microscopy （SEM） （Cambridge， Leica） with an accelerating voltage value equal to 15 kV． The samples， analyzed in their cross section， were coated with a thin gold layer by means of a sputter coating （Polaron， model SC502 sputter coater） ［21］．
DSC is one of the most convenient approaches to throw light on the degree of crystallinity along with the thermal behavior of any polymeric samples ［4］．The glass transition temperature （T g ） of the resulting polymer film was determined via DSC measurement． The T g of a polymer indicates the transition from a rubbery into a glassy state． Therefore， the polymer is flexible above the T g and hard and brittle below the T g ［21］．
In our study， DSC analysis was carried out with a Mettler Differential Scanning Calorimeter instrument （Figure 1. 5. ） under argon purge atmosphere flow （70. 0 mL／ min） ［75］ between －100 ℃ and 150 ℃ along with liquid nitrogen as a cooling element ［34］． Samples around 5 ～ 7mg were sealed in 40 μL aluminum pans with perforated lids to allow the release and removal of the decomposition products ［20］． Two segments of DSC scanning included：1）－100 ℃ isothermal for 10. 0 min， 2） with a heating rate of 10 ℃ ／ min and the temperature range from －100 to 150 ℃ ． Another empty aluminum pan was placed as a reference．
Figure 1. 5. A schematic of DSC experiment
The thermal stability of the polymer electrolytes was measured by thermogravimetric analysis （TGA）． Thermogravimetric measurement was carried out with a TGA／ SDTA851e thermal analyzer． Around 5. 442 mg of sample were placed in a TGA aluminum pan． The sample was heated from 25 ℃ to 130 ℃for 15 minutes and cooled rapidly to 25 ℃ for 15 min． Then the samples were heated up to 400℃ at a rate of 10 ℃ ／ min ［12］． The fully amorphous nature of the polymer was observed under thermal characterization．
The electrochemical stabilities of the SPE membranes were determined by cyclic voltammetry （CV） using a potentiostat ／ galvanostat （Solartron impedance analyzer）． A testing cell was assembled to determine the oxidation potential with stainless steel as working electrode and lithium foil serving as a counter and reference electrode． All the scans were made at 25 ℃ at a scan rate of 10 mV／ s within a voltage range of 0 V to 5. 0 V versus Li ／ Li ＋ ［76］．
The ionic conductivity of the obtained compounds was measured by the complex impedance method using an impedance analyzer （Solartron model SI1287； Schlumberger） coupled to a Solartron model-1260 frequency response analyzer． The membranes were sandwiched between two stainless steel electrodes of 2. 54 cm 2 in the area for conductivity measurement ［77］． All the measurement was performed in a glove box filled with a dry nitrogen gas in a temperature range of 25 －70 ℃ ［78］．
The ionic conductivity （δ， in S cm － 1 ） was plagiaristic from the value of resistance （R， in Ω） of the bulk electrolyte obtained in the complex impedance diagram， in relation to the equation： δ ＝ L／ （RS）， where L （cm） is the thickness of the membrane of the polymer electrolyte， and S （cm 2 ） is the area of the membrane ［22］．