Gang Huang,Xi-ao Yan,Rongrui Shi,Jing Sun,Qiang Fang
With the rapid development of high speed and high frequency communication, organic low dielectric (low- k ) materials with both ultra-low dielectric constant ( D k ) and ultra-low dielectric loss ( D f ) are urgently required to ensure signal transmission speed and reliability. 1,2-polybutadiene ( 1,2-PB ) is renowned for its excellent dielectric properties, making it used in high-frequency printed circuit boards (PCBs). However, its poor thermal stability and mechanical properties hinder its application which requires persistent stability. To address this issue, a series of thermal-crosslinkable benzocyclobutene (BCB)-modified PBs were synthesized through a hydrosilylation reaction. These cured PBs exhibited significantly enhanced thermal stability with the glass transition temperature ( T g ) exceeding 400 °C. In particular, they displayed ultra-low D k (2.32–2.41) and ultra-low D f (<0.001). It was found that the properties of cured PBs were related to BCB loadings. Among the cured polymers, PB- g -B 30 demonstrated the optimal dielectric properties with a D k of 2.34 and a D f of 3.6 × 10 −4 . Subsequently, a PB- g -B 30 /glass fiber laminate was fabricated, exhibiting superior dielectric and comprehensive properties when compared to commercial low- k laminates. This study provides a facile method to develop PBs with ultra-low D k and D f and enhanced thermal stability. The outstanding comprehensive properties indicate their potential as low- k materials in high-frequency communication applications.
Two-way shape memory polymers (2W-SMPs), which can transition between two distinct temporary shapes, have garnered significant attention from researchers. This study successfully developed thermadapt 2W-SMPs using syndiotactic 1,2-polybutadiene (SPB) by leveraging dynamic covalent crosslinking techniques. Initially, m-chloroperbenzoic acid (m-CPBA) was employed for the epoxidation of SPB. Cysteine (Cys) was subsequently introduced to form a dynamic covalent bond of β -hydroxy ester via the reaction between the epoxy groups on SPB and the carboxyl groups of Cys. The sulfhydryl groups of Cys can undergo oxidative coupling to form disulfide bonds, thereby establishing two distinct types of dynamic covalent bonds within the material and lowering its topological rearrangement temperature. Through the exchange reactions of these dynamic covalent bonds at elevated temperatures, the resulting material exhibits enhanced mechanical properties and can be reshaped in the solid state. This work provides a viable method for preparing recyclable thermally adaptive 2W-SMPs under stress-free conditions, thereby enriching the research landscape in the field of shape memory materials.
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