A highly flexible and stretchable all-solid-state supercapacitor that can bear a tensile strain as high as 480% is developed by using composite electrodes of aligned carbon nanotube and silver-doped poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate).

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In this work, to obtain a novel composite hydrogel with high mechanical strength, fluorescence and degradable behavior for bone tissue engineering, we prepare a nanofiller and double-network (DN) structure co-enhanced carbon dots/hydroxyapatite/poly (vinyl alcohol) (CDs/HA/PVA) DN hydrogel. The composite hydrogels are fabricated by a combination of two fabrication techniques including chemical copolymerization and freezing‒thawing cycles, and further characterized by FTIR, XRD, etc. Additional investigations focus on the mechanical properties of the hydrogel with varying mass ratios of CDs to PVA, HA to PVA and different numbers of freezing/thawing cycles. The results show that the as-prepared CDs3.0/HA0.6/PVA DN9 hydrogel has optimized compression properties (Compression strength = 3.462 MPa, Young’s modulus = 4.5 kPa). This is mainly caused by the synergism effect of the nanofiller and chemical and physical co-crosslinking. The water content and swelling ratio of the CDs/HA/PVA SN and DN gels are also systematically investigated to reveal the relationship of their microstructural features and mechanical behavior. In addition, in vitro degradation tests of the CDs/HA/PVA DN hydrogel show that the DN hydrogels have a prominent degradable behavior. So, they have potential to be used as high-strength, self-tracing bone substitutes in the biomedical engineering field.

1 Silicon-containing aryacetylene resins (PSAs) have already shown potential 2 application as heat-resistant materials due to their excellent thermal stability. The 3 formation and degradation of structures in cured PSAs are very important to evaluate 4 the thermal properties during their applications. Herein, the thermal curing and 5 degradation behavior of PSAs with different substituents were investigated by DSC, 6 FT-IR, Py-GC-MS, TGA and TG-GC-MS. DSC and FT-IR analysis reveals that the 7 curing reaction is dominated by the crosslinking reaction of C≡C-H and Si-C≡C-, 8 meanwhile, the reactive substituents (such as Si-H and Si-CH=CH 2 ) could promote 9 the C≡C-H and Si-C≡C-reaction with higher conversion. Py-GC-MS was used to 10 detect the pyrolysis products at 650℃ and 750℃, respectively, and the results could 11 provide important information about the curing reaction and structures of cured PSAs. 12 The curing reaction of PSAs mainly contains cyclotrimerization and Diels-Alder 13 reaction of C≡C-H and Si-C≡C-, and some addition reaction to form polyene structure. 14 The main structures in cured PSAs contain a lot of phenyl rings, some aromatic fused 15 rings and a little of polyene structure, moreover, their contents in cured PSAs are 16 dependent on the substituents of the precursors. The TGA results show that the 17 substituents of Si-H and Si-CH=CH 2 can effectively improve the crosslinking index 18 of the cured PSA-H and PSA-V, and endow them with better thermal stability. 19Additionally, the degradation behavior of cured PSAs have been well studied by 20 TG-GC-MS. When the temperature is 400℃, the Si-CH 3 and some aliphatic structure 21 begin to degrade and form CH 4 , and with the temperature increasing to 500℃, the 22 unsaturated and aliphatic structures decompose into C 2 H 4 and C 2 H 6 , and after 600℃, 23 the aromatic rings and fused rings in cured PSAs are dehydrogenated and release H 2 . 24In addition, the content of the degradation products and their forming temperature are 25 also related with the substituents. 26 27 Key words： 28 Silicon, arylacetylene, cure, degradation 29 3 1

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