Benzocyclobutene Groups Research Articles

A "Bottom-Up" Strategy for High-Performance Benzocyclobutene (BCB)-Subnanometer Inorganic Nanocomposites.

Developing benzocyclobutene (BCB) nanocomposites with ultra-small inorganic sizes represents a formidable challenge, although it offers great potential to produce materials with customizable structural and rich functional properties. In this study, we present a "bottom-up" design strategy for creating cross-linked benzocyclobutene (BCB) nanocomposites with highly dispersed nanodomains, such as organoalkoxysilane. This approach leverages ring-opening metathesis polymerization (ROMP) and thermally induced cycloaddition reactions to embed oligomeric silsesquioxanes, achieving a unique molecular structure with promising low-dielectric applications. The synthesis involves organoalkoxysilane and BCB as pendant groups of polynorbornenes that are covalently integrated. Additionally, the methoxyl groups of linear polymers could be further hydrolyzed under acidic conditions, and BCB groups could undergo thermal-induced ring-opening at high temperatures and Diels-Alder addition between themselves and vinyl groups, respectively. Fourier transform infrared (FTIR) spectroscopy analyses suggested the presence of ladder or network structures and high-resolution transmission electron microscopy (HRTEM) images presented the well-dispersed inorganic clusters, facilitating excellent dielectric properties with a dielectric constant (Dk) of 2.25 and a dissipation factor (Df) of 2.27 × 10-4. Compared with previously reported low-Dk materials, the cured nanocomposites also exhibited a significantly balanced enhancement of their comprehensive properties. This molecular bottom-up strategy provided a simple and universal method for constructing BCB-inorganic nanocomposites featuring a subnanometer inorganic structure, paving the way for future investigation into new classes of polymer-inorganic nanocomposites with a low Dk.

A bio-based low dielectric polymer at high frequency derived from paeonol

A fluorinated monomer with crosslinkable benzocyclobutene groups has been successfully synthesized starting from bio-based paeonol through the Suzuki and Grignard reaction. Treating this monomer at high temperature forms a cross-linked resin (cured PFB), which exhibits high glass transition temperature (Tg) of 439 °C, low coefficient of thermal expansion (CTE) of 87.4 ppm/°C, low dielectric constant (Dk) of 2.62, and low dielectric loss (Df) of 8.45 × 10-4 at a frequency of 10 GHz. In particular, cured PFB displays low water uptake of 0.1% even immersing it in boiling water for 96 h. These results demonstrate that the fluorinated bio-based monomer is a suitable precursor for the preparation of the low-dielectric packaging materials used in the microelectronic industry. Especially, this contribution provides a new way for the conversion of bio-based paeonol into the high-performance materials.

Low-temperature thermal cross-linkable materials with benzocyclobutene groups for solution process of OLEDs

Three novel cross-linkable hole injection materials were designed and synthesized herein. Effective cross-linking was observed for small molecules that incorporate the benzocyclobutene groups at a low temperature of 130 °C or less. These compounds exhibited good solubility in common organic solvents and excellent solvent resistance after cross-linking at a low temperature of 130 °C. The OLED was successfully fabricated using a mixture prepared by adding 4-Isopropyl-4'-methyldiphenyliodonium Tetrakis(pentafluorophenyl)borate (TPFB) to the newly synthesized cross-linkable material as HIL. Maximum current and power efficiencies are 52.92 cd/A and 19.67 lm/W, respectively. The study is expected to accelerate the development of low-temperature cross-linkable materials for solution-processed OLEDs.

Highly heat-resistant polymers with good dielectric properties at high frequency derived from a bio-based resveratrol

Starting from a bio-based resveratrol, a new monomer (M1) without oxygen atoms and having thermocrosslinkable benzocyclobutene groups and a double bond has been obtained. Thermally cured M1 displays excellent heat resistance with a 5% weight loss temperature (T5d) of 532 °C, a glass transition temperature (Tg) of higher than 400 °C, a very high char yield of 79% at 1000 °C and a very low coefficient of thermal expansion (CTE) of 18.2 ppm/°C. For comparison, a control monomer (M2) has been prepared by hydrogenating the double bond of M1. Thermally cured M2 exhibits excellent dielectric properties with dielectric constant (Dk) of 2.75 and dielectric loss (Df) of 7 × 10−4 at a high frequency of 5 GHz. These results mean that the double bonds in the molecule endow the polymers with higher thermostability, while the alkyl group makes the Dk and Df polymers decreased. In contrast, the polymers containing oxygen atoms derived from resveratrol (cured M3 and cured M4) exhibit increased Dk and Df, and lowered thermostability. This work provides a helpful way to design the materials with high heat-resistance and low dielectric properties for the application in aerospace and microelectronic industry.

Bio-based Low-k Polymers at High Frequency Derived from Anethole: Synthesis and the Relationship between the Structures and the Properties.

Bio-based polymers have been widely investigated as sustainable low dielectric (low-k) materials in past decades. Nevertheless, a few of the polymers with excellent comprehensive properties have been achieved to satisfy the requirements of high-frequency communication application. In this paper, two fluorinated monomers (BCB-F and 2BCB-F) have been designed and successfully prepared from biomass anethole. The thermal-cross-linkable benzocyclobutene and polyfluorobenzene groups were introduced in order to obtain low-k polymers with good comprehensive properties. A control monomer C1 was prepared from the estragole, the isomer of anethole, to study intensively the effect of structures on properties. Among the thermally cured polymers, cured BCB-F with higher fluoride content shows a comparable dielectric constant (Dk) of 2.62 and lower dielectric loss (Df) of 1.31 × 10-3 at a frequency of 10 GHz, as well as better hydrophobic properties with a water uptake of 0.18%. Such good hydrophobic properties enable it to maintain the good dielectric properties even after being soaked in boiling water for 96 h. Cured 2BCB-F with bifunctional benzocyclobutene groups displays excellent heat resistance with a high glass transition temperature (Tg) of 408 °C and a low coefficient of thermal expansion (CTE) of 52 ppm/°C in the temperature range 30-300 °C. Cured 2BCB-F also shows good dielectric properties with a Dk of 2.61 and a Df of 2.60 × 10-3 at a frequency of 10 GHz. The good comprehensive properties reveal that the anethole-based polymers are suitable candidates as matrix or encapsulation resins for application in electronics and microelectric fields.

Solvent-Free Templated Synthesis of Core-Crosslinked Star-Shaped Polymers in Supramolecular Body-Centered Cubic Phase.

This study reports the exploration of a solvent-free supramolecular templated synthesis strategy toward highly core-cross-linked star-shaped polymers (CSPs). To achieve this, a kind of cross-linkable giant surfactant, based on a functionalized polyhedral oligomeric silsesquioxanes (POSS) head tethered with a diblock copolymer tail containing reactive benzocyclobutene groups, is designed and prepared. By varying the volume fraction of linear block copolymer tail, these giant surfactants can self-assemble into a body-centered cubic (BCC) structure in bulk, in which the supramolecular spheres are composed of a core of POSS cages, a middle shell of crosslinkable poly(4-vinylbenzocyclobutene) (PBCB) blocks, and a corona of inert polystyrene (PS) blocks. The solvent-free thermally induced cross-linking reaction of the benzocyclobutene groups can be finished in 5min upon heating, resulting in well-defined polymeric spheres with over 90 linear chains surrounding the cross-linked cores. The outer PS blocks serve as the protection corona to ensure that cross-linking of giant surfactants occurs in each supramolecular spherical domain. Given the modular design and diversity of the POSS-based giant surfactants, it is believed that the strategy may enable access to a wide range of CSPs.

The low dielectric constant hyperbranched polycarbosilane derived resins with spacing groups

AbstractThe route via the cross‐linking of hyperbranched prepolymers has potential advantage to construct low dielectric constant (low‐k) resins owing to the enhanced molecular free volume in hyperbranched structure. However, it is still a challenge to prepare hyperbranched resins with good film‐forming property and low‐k. In this paper, two hyperbranched polycarbosilanes with reactive benzocyclobutene groups were synthesized via hydrosilylation reaction to avoid the generation of SiO bonds for enabling the low polarity of chemical bonds. The spacing groups including phenyl or ethylene were incorporated into the hyperbranched structures, and the effect of the spacing groups on the physicochemical properties of hyperbranched polycarbosilane derived resins were investigated. The phenyl groups were found to effectively decrease the dielectric constant (k), while endowing the resins with good film forming ability and thermostability. The UV/thermally cured phenyl group resin owing to dual crosslinked structure, the patterns would not be deformed significantly during thermally cured process. Both hyperbranched polycarbosilane derived resins could be potential photoresists.

UV-curable low dielectric siloxane-benzocyclobutene resins via introducing carbosilane groups

• New UV-curable low dielectric siloxane-benzocyclobutene oligomers ( SBCOs ) on the basis of carbosilane groups were prepared. • The oligomeric SBCOs have a UV/thermally dual crosslinked structure. • Cured siloxane-benzocyclobutene resins exhibited high thermostability, mechanical strength, and low dielectric properties. Low dielectric UV-curable resins are compatible with photolithography and 3D printing technique, and have great potential for use in inter-layered packaging and antenna. However, it is still a challenge to construct photoactive structure which combines low dielectric properties. In the present work, we propose a new type of low dielectric UV-curable resins by employing photoactive silacyclobutene groups. This low dielectric resins were prepared by UV/thermally curing of siloxane-benzocyclobutene oligomers (SBCOs). Oligomeric SBCOs were prepared by the simple hydrolysis-polycondensation of 1,1-dichlorosilacyclobutane followed by termination of the benzocyclobutene groups. In this way, silaycyclobutene and benzocyclobutene groups were simultaneously introduced into the resins to enable UV and thermally curing of SBCOs. The molecular weight of SBCOs were tuned by the ratio of 1,1-dichlorosilacyclobutane and benzocyclobutene-containing monomer. The cured siloxane-benzocyclobutene resins were thermostable, mechanically strong, and had low dielectric properties.

Low dielectric resins derived from hyperbranched carbosilane oligmers functionalized by benzocyclobutene groups

ABSTRACT Polycarbosilanes have been considered as potential materials used in electronic packaging and circuit boards owing to their excellent low-dielectric performance. In this work, we prepared new hyperbranched carbosilane oligomers (HCBOs) which were functionalized by benzocyclobutene (BCB) groups. HCBOs can be thermally cured to produce transparent (HCBRs) with low dielectric constant and high thermostability.

A Fluorinated Thermocrosslinkable Organosiloxane: A New Low-k Material at High Frequency with Low Water Uptake.

In order to obtain low-k material with good comprehensive properties, a trifluoromethyl-containing organosiloxane with thermocrosslinkable vinyl and benzocyclobutene groups is designed and synthesized through the Piers-Rubinsztajn reaction. After treating at high temperature, the organosiloxane changed to form a cross-linked polysiloxane (called as c-FSi-BCB). c-FSi-BCB exhibits good dielectric properties with dielectric constant (Dk ) of 2.60 and dielectric loss (Df ) of 1.49 × 10-3 at a high frequency of 5GHz. Importantly, c-FSi-BCB maintains such good dielectric properties and exhibits low water uptake of below 0.076%, even after immersing it in boiling water for 96 h. c-FSi-BCB also displays good thermostability with a 5% weight loss temperature (T5d ) of 453 °C. These data indicate that this fluorinated organosiloxane is suitable as the matrix resin for the fabrication of devices used in 5G communication.

Preparation of planar and hydrophobic benzocyclobutene‐based dielectric material from biorenewable rosin

ABSTRACTA rosin‐based monomer with thermally crosslinkable benzocyclobutene groups was synthesized in this study. The structure of the monomer was examined using mass spectroscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. An amorphous crosslinked network with dielectric constant of 2.71 and dielectric loss of 0.0012 at 30 MHz was formed when the monomer was polymerized at high temperature (> 200 °C). The polymer film exhibits surface roughness (Ra) of 0.337 nm in a 5.0 × 5.0 μm2 area and the water contact angle of 110°. In addition, results from thermogravimetric analysis indicate that the polymer has T5% = 402 °C, and differential scanning calorimetry measurements show that the glass transition temperature is at least 350 °C. Results from nanoindentation tests show that the hardness and Young's modulus of the polymer are 0.418 and 4.728 GPa, respectively. These data suggest that this new polymer may have potential applications in electronics and microelectronics. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48831.

Postpolymerization of a fluorinated and reactive poly(aryl ether): an efficient way to balance the solubility and solvent resistance of the polymer.

A new fluorinated poly(aryl ether) with reactive benzocyclobutene groups as the side chain was successfully synthesized. This polymer showed a number-average molecular weight (Mn) of 200,000 and had good solubility and film-forming ability. After being postpolymerized at high temperature (>200 °C), the polymer film converted to a cross-linked network structure, which was insoluble in the common organic solvents. Such results suggest that the postpolymerization is an efficient way to achive the balance between the solubility and the solvent resistance of the polymer. TGA data showed that the postpolymerized polymer had a 5 wt % loss temperature at 495 °C and a residual of 61% at 1000 °C under N2. The cross-linked film also exhibited good dielectric properties with an average dielectric constant of about 2.62 in a range of frequencies from 1 to 30 MHz. With regard to the mechanical properties, the cross-linked film had hardness, Young's modulus, and bonding strength to a silicon wafer of 1.22, 8.8, and 0.89 GPa, respectively. These data imply that this new polymer may have potential applications in the electrical and microelectronics industry.

Synthesis and thermal polymerization of perylene bisimide containing benzocyclobutene groups

Abstract Fourfold benzocyclobutene-functionalized perylene bisimide (PBI 4) has been synthesized and its structure was characterized by FTIR, MS and NMR. PBI 4 can react either with itself, or the appropriate dienophiles to form the corresponding products under appropriate temperature. The polymer film obtained from the reaction of PBI 4 with methyl vinyl silicone rubber possessed excellent film forming properties including flatness. The optical properties of PBI 4 and polymer film obtained from the reaction of PBI 4 and methyl vinyl silicone rubber have been determined by UV/vis and fluorescence spectroscopy.

Greatly Enhanced Thermal Contraction at Room Temperature by Carbon Nanotubes

A crosslinked polyarylamide polymer exhibits novel photothermal behavior, that is, reversible giant contraction in response to near infrared irradiation in addition to normal thermal expansion. Such reversibility is seldom found in a polymeric system. Due to the amphiphilic nature of the benzocyclobutene‐containing triblock copolymer precursor with polyarylamide interacting strongly with few‐walled carbon nanotubes (FWCNTs), they are dispersed extremely well in the polymer solution at a loading up to at least 5 wt%. Also, strained carbon double bonds on FWCNTs can directly form covalent linkages with the benzocyclobutene groups on the polymer chains via cyclo‐addition. The incorporation of FWCNTs increases mechanical stiffness two‐fold. Exploiting the ability of FWCNTs to effectively convert photon energy into heat and to provide conductive pathways, the NIR‐induced unexpected contraction stress can be further increased dramatically. The systematic study suggests that there is an optimal CNT concentration. At 3 wt% FWCNTs, the enhancement factor for contraction stress is almost 24: 166 kPa with 3 wt% FWCNTs versus 7 kPa without FWCNTs. The colossal photothermal contraction stress generated by this new composite film at ambient condition upon NIR stimulation can lead to the development of new NIR actuators, for example, for biological applications, and create new material platforms for green energy conversion.

A new low dielectric material with high thermostability based on a thermosetting trifluoromethyl substituted aromatic molecule

A thermally cross-linkable molecule composed of bis(trifluoromethyl)benzene and benzocyclobutene units (F1) was successfully prepared. Heating F1 (>200 °C) gave a cured resin, which showed a dielectric constant (k) of 2.47 at 30 MHz and an average k value of less than 2.51 in a range of frequencies from 0.15 MHz to 30 MHz. Such low k values are comparable to other polymeric low-k materials. For comparison, a perfluorobenzene with benzocyclobutene groups (F2) was also synthesized. The cured F2 exhibited an average k value of 2.98, indicating that the introduction of a trifluoromethyl group into the backbone of the molecules can efficiently decrease the dielectric constant of the molecules. The cured F1 also exhibited high thermostability (T5 = 429 °C, weight residual = 47.7% at 1000 °C under N2). These results suggest that F1 is suitable for the utilization in ultra large scale integration circuits.

Synthesis and characterization of siloxane resins derived from silphenylene‐siloxane copolymers bearing benzocyclobutene pendant groups

AbstractTwo bis(dimethylamimo)silanes with benzocyclobutene (BCB) groups, bis(dimethylamino)methyl(4′‐benzocyclobutenyl)silane (2) and bis(dimethylamino)methyl [2′‐(4′‐benzocyclobutenyl)vinyl]silane (4), were synthesized from different synthetic routes, which were then employed to prepare two novel silphenylene‐siloxane copolymers (SiBu and SiViBu) bearing latent reactive BCB groups by polycondensation procedure with 1,4‐bis(hydroxydimethylsilyl)benzene. At elevated temperatures these copolymers were readily converted to highly crosslinked films and molding disks with network structures by polymer chain crosslinking, which followed the first‐order kinetic reaction model. The final resins of SiBu and SiViBu demonstrated excellent thermal stability with high glass transition temperatures (218 and 256 °C) and high temperatures at 5% weight loss (553 and 526 °C in N2, 530 and 508 °C in air). After aging at 300 °C in air for 100 h, the cured resins showed weight loss lower than 4%. The films of cured SiBu and SiViBu also exhibited relatively low dielectric constants of 2.66 and 2.64, low dissipation factors of 2.23 and 2.12 × 10−3, low water absorptions (≤0.28%), and high transparence in the visible region with cutoff wavelengths of 321 and 314 nm. Moreover, the aged films exhibited good dielectric properties and low water absorptions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7868–7881, 2008

A facile approach to architecturally defined nanoparticles via intramolecular chain collapse.

A novel approach is presented for the controlled intramolecular collapse of linear polymer chains to give well-defined single-molecule nanoparticles whose structure is directly related to the original linear polymer. By employing a combination of living free radical polymerization and benzocyclobutene (BCB) chemistry, nanoparticles can be routinely prepared in multigram quantities with the size being accurately controlled by either the initial degree of polymerization of the linear chain or the level of incorporation of the BCB coupling groups. The latter also allows the cross-link density of the final nanoparticles to be manipulated. In analogy with dendritic macromolecules, a significant reduction of up to 75% in the hydrodynamic volume is observed on going from the starting random coil linear chains to the corresponding nanoparticles. The facile nature of the living free radical process also permits wide variation in monomer selection and functional group incorporation and allows novel macromolecular architectures to be prepared. Furthermore, the use of block copolymers functionalized with benzocyclobutene groups in only one of the blocks gives, after intramolecular collapse, a hybrid architecture in which a single linear polymer chain is attached to the globular nanoparticle.

Production of crosslinked, hollow nanoparticles by surface‐initiated living free‐radical polymerization

AbstractSurface‐initiated living free‐radical polymerization is employed in a multistep procedure to prepare hollow polymeric nanocapsules. Initially, trichlorosilyl‐substituted alkoxyamine initiating groups are attached to the surface silanol groups of silica nanoparticles. This surface layer of initiating groups is then used to grow functionalized linear chains leading to a core–shell morphology. The choice of functional groups is governed by their ability to undergo facile crosslinking reactions, with both active ester and benzocyclobutene groups being examined. Under either chemical or thermal conditions, the reaction of these functionalities gives a crosslinked polymeric shell that is covalently attached to, and surrounds, the central silica core. Removal of the silica core with HF then gives the hollow polymeric nanocapsules, which are stable under solvent dissolution and thermal treatment because of their crosslinked structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1309–1320, 2002

Polybenzobisthiazoles with crosslinking sites for improved fibre axial compressive strength

A number of homo- and copolymer benzobisazole rigid-rod polymers have been synthesized, containing labile methyl pendants and benzocyclobutene groups for thermally induced crosslinking studies. Polycondensations of tetraamino, diaminodihydroxy and diaminodithio monomers with methyl, dimethyl and benzocyclobutene terephthalic acid derivatives in polyphosphoric acid (PPA) provided high molecular weight anisotropic liquid crystalline reaction mixtures. Selected benzobisthiazole polymers were dry-jet wet-spun into fibres from these PPA solutions. Depending on their thermal treatment conditions, the fibres showed Young's moduli from 18 to 43 Msi (124–296 GPa) and tensile strengths from 240 to 460 Ksi (1650–3170 MPa), comparable to those of unsubstituted benzobisazole rigid-rod polymer fibres. The highest axial compressive strength obtained from these fibres was 70 Ksi (480 MPa), a marginal improvement over that of unsubstituted rigid-rod polymer fibres.

Microstructure of Thermally Crosslinkable Poly(Ethylene Terephthalate) (Pet-co-Xta) Benzocyclobutene Functionalized Copolymers

ABSTRACTThe microstructure and thermal properties of copolymers of polyethylene terephthalate (PET) containing a crosslinkable terephthalic acid, 1,2-dihydrocyc Iobutabenzene 3,6 dicarboxylic acid (XTA) are reported. Wide angle x-ray scattering (WAXS) show that the addition of XTA does not alter the PET crystal structure in copolymers at low XTA contents. However, the degree of crystallinity drops for higher XTA levels. WAXS profiles show that PET-co-XTA 50% is amorphous, and that PEXTA homopolymer has a different crystal structure. Thermal data from DSC and TGA show that crosslinking of the benzocyclobutene groups (∼350°C) occurs at temperatures between melting (∼250°C) and degradation (∼400°C), making it possible to melt process the copolymers into fibers before the onset of crosslinking. Limiting oxygen index (LOI) measurements show that increased oxygen concentrations are required to sustain a stable flame in PET-co-XTA copolymers; whereas unmodified PET had an LOI value of -18%, the copolymers had LOI values near 32%. Further, while unmodified PET melts and drips as it burns, XTA copolymers formed a stable char that inhibiting flame propagation. An increased char was observed in optical micrographs for XTA containing polymers, and crystalline domains were observed near the burn surface in transmission electron micrographs.