Preparation and Properties of Low Dielectric Constant Siloxane/Carbosilane Hybrid Benzocyclobutene Resin Composites

Benzocyclobutene-modified silsesquioxane (BCB-POSS) and divinyl tetramethyl disiloxane-bisbenzocyclobutene (DVS-BCB) prepolymer were introduced into the containing benzocyclobutene (BCB) unit matrix resin P(4-MB-co-1-MP) polymerized from 1-methyl-1-(4-benzocyclobutenyl) silacyclobutane (4-MSCBBCB) and 1-methyl-1-phenylsilacyclobutane (1-MPSCB), respectively. The low dielectric constant (low-k) siloxane/carbosilane hybrid benzocyclobutene resin composites, P(4-MB-co-1-MP)/BCB-POSS and P(4-MB-co-1-MP)/DVS-BCB, were prepared. The curing processes of the composites were assessed via Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The effects on dielectric properties and heat resistance of those composites with different proportion of BCB-POSS and DVS-BCB were investigated using an impedance analyzer and thermogravimetric analyzer (TGA), respectively. The thermal curing of composites could be carried out by ring-opening polymerization (ROP) of the BCB four-member rings of BCB-POSS or DVS-BCB and those of P(4-MB-co-1-MP). With increasing the proportion of BCB-POSS to 30%, the 5% weight loss temperature (T_5%) of P(4-MB-co-1-MP)/BCB-POSS composites was raised visibly, whereas the dielectric constant (k) was decreased owing to the introduction of nanopores into POSS. For P(4-MB-co-1-MP)/DVS-BCB composites, the T_5% and k were slightly raised with increasing the proportion of DVS-BCB. The above results indicated that the BCB-POSS showed advantages over conventional fillers to simultaneously improve thermostability and decrease k.

Benzocyclobutene-functionalized hyperbranched polysiloxane for low-k materials with good thermostability

Although hyperbranched polysiloxanes have been extensively studied, they have limited practical applications because of their low glass transition temperatures. In this study, we synthesized benzocyclobutene-functionalized hyperbranched polysiloxane (HB-BCB) via the Piers-Rubinsztajn reaction. The synthesized material was cured and crosslinking occurred at temperatures greater than 200 °C, forming a low-k thermoset resin with high thermostability. The structure of the resin was characterized using nuclear magnetic resonance (NMR) spectroscopy, viz. ¹H NMR and ¹³C NMR spectroscopy. ²⁹Si NMR spectroscopy was used to calculate the degree of branching. Differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis revealed that the cured resin possesses good high-temperature mechanical properties and exhibits a high thermal decomposition temperature (T_d5 = 512 °C). In addition, the cured resin has a low dielectric constant (k = 2.70 at 1 MHz) and low dissipation factor (2.13 × 10^-3 at 1 MHz). Thus, the prepared resin can function as a low-k material with excellent high-temperature performance. These findings indicate that the performance of crosslinked siloxane is significantly attributed to the introduction of BCB groups and the formation of the highly crosslinked structure.

RECYCLING BEHAVIOR OF THERMOREVERSIBLY DIELS–ALDER CROSSLINKED EPM

The recyclability of thermoreversibly Diels–Alder (DA) crosslinked EPM has been studied. The retro DA reaction dominates over the dehydration–aromatization process of the DA adduct. Moreover, a negative influence of air occurred as a result of a crosslinking in air flow. Nevertheless, rubber compounds prepared from EPM-g-furan and carbon black can be recycled several times without losing mechanical strength, a feature attributed to a strong antioxidant effect of the carbon black.

Recyclability of Photoinduced Cross-Linked EPM Rubber with Anthracene-Grafted Groups: Problems and Their Solutions

In this paper, we present the formation of reversible covalently cross-linked networks in ethylene propylene rubber with grafted anthracene groups (EPM-g-AN) based on the principles of photoinduced anthracene dimerization. First, an industrial-grade EPM rubber grafted with maleic anhydride functional groups (EPM-g-MA) was modified with 9-anthracenemethanol. By irradiating EPM-g-AN with UV light (365 nm), the anthracene moieties dimerize via [4 + 4]cycloaddition, forming a covalent network. The network cleavage proceeds at high temperatures (>170 °C), even if with considerable (chemical) degradation. Furthermore, one of the degradation routes has been identified by ¹H NMR to occur via the ester bond cleavage releasing 9-anthracenemethanol. Nevertheless, the reversibility of cross-linking has been achieved by performing the reverse reaction in decalin. The UV-vis spectroscopy clearly shows that the de-cross-linking process in these conditions is due to the anthracene dimer cleavage. Although the recovery in mechanical properties upon recycling is yet to be optimized, the disclosed results pave the way toward the use of anthracene chemistry in thermally reversible networks with possible industrial perspective applications.

Bicyclo[4.2.0]octa-1,3,5-trien-3-yl-dimethyl((E)-styryl)-silane

Bicyclo[4.2.0]octa-1,3,5-trien-3-yl-dimethyl-((E)-styryl)-silane was synthesized via three stage synthesis starting from benzocyclobutene and (2-bromo-vinyl)-benzene. The structure of the product was determined using 1H- and 13C-NMR and HRMS.

Biorenewable rosin derived benzocyclobutene resin: a thermosetting material with good hydrophobicity and low dielectric constant

Development of bio-based polymers has been promoted by the growing concerns about the long-term sustainability and negative environmental footprint of petroleum-based polymer materials. A new monomer containing benzocyclobutene and allyl units has been developed by using rosin as the feedstock. The structure of the monomer was characterized by elemental analysis, MS, FT-IR and NMR spectroscopy. The monomer could be converted to the polymer via thermal ring-opening polymerization which was characterized via FT-IR, thermogravimetric analysis (TGA), atom force microscopy (AFM) and so on. The polymer showed good dielectric properties and hydrophobicity with an average dielectric constant of 2.51 in a range of frequencies from 0.1 to 18 MHz and a water contact angle of 106°. In addition, the polymer with other comprehensive performances exhibited a 5% weight loss temperature of 406 °C, a surface roughness (R_a) of 0.658 nm in a 5.0 × 5.0 μm² area, hardness and Young's modulus of 0.283 and 3.542 GPa, and storage modulus of 11.46 GPa at 30 °C. These data suggest that the polymer may have potential application in electronics and microelectronics.

The rosin structure was introduced into benzocyclobutene resin for the first time, and the thermosetting material with good hydrophobicity and low dielectric constant was prepared.

Self-crosslinkable and modifiable polysiloxanes possessing Meldrum's acid groups

Meldrum's acid functionalized poly(dimethylsiloxane)s exhibiting self-crosslinking and post-modifiable features.