Maleimide-based resin

Uncatalyzed Diels-Alder reactions and [2 + 3]-heterodipolar cycloadditions can be performed on a variety of acrylic or maleimide-based resins. One simple method is to link an acrylic residue to a polymeric support via an ester or an amide linkage. 

As already mentioned, aromatie polymers are thermally stable but aliphatic portions of them are not as thermally stable. Typical maleimide resins have aliphatic units. This is inevitable because the Michael addition was used to prepare the maleimide-based oligomers. On the other hand, if an adhesive consists of a linear thermoplastic polymer, it is not usable at temperatures above its softening temperature. Introdueing chemical crosslinking is one way to prevent thermal weakening of a material. 

Another multifunctional amide-containing linker has also been published recently by Abell et al. [180]. The synthesis of the new anthracenyl-based linker 168 involves again four synthetic steps in solution phase that can be conducted in 53% overall yield. Different to the other linker strategies is the attachment to the resin because the linker core and the substrate are connected in solution phase and are afterwards linked to a maleimide-polystyrene resin. To prove the utility of the new resin, N- and 0-nucleophiles were added to give amides 171, esters 170 and carboxylic acids 169 (Scheme 26). 

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

One can vary the chemical composition of the bis-maleimide system by replacing tbe MDA with other diamines. The nature of the resin is not that different from that using MDA because the resins are so highly crosslinked. Based upon availability, ease of use and cost, BMI and MDA are most often used. However, one commercial maleimide resin, Techocbemie s Compimide H795 has an original structure. As shown in Fig. 8, it is composed of BMI and / -aminobenzoyl hydrazide [10]. 

In 2001, Sarko and coworkers disclosed the synthesis of an 800-membered solution-phase library of substituted prolines based on multicomponent chemistry (Scheme 6.187) [349]. The process involved microwave irradiation of an a-amino ester with 1.1 equivalents of an aldehyde in 1,2-dichloroethane or N,N-dimethyl-formamide at 180 °C for 2 min. After cooling, 0.8 equivalents of a maleimide dipo-larophile was added to the solution of the imine, and the mixture was subjected to microwave irradiation at 180 °C for a further 5 min. This produced the desired products in good yields and purities, as determined by HPLC, after scavenging excess aldehyde with polymer-supported sulfonylhydrazide resin. Analysis of each compound by LC-MS verified its purity and identity, thus indicating that a high quality library had been produced. 

Heat resistant resin compositions based on BMI/aminophenol-Epoxy blends are achieved by reacting a BMI/p-aminophenol 1 1 adduct with epoxy resin (62). Both the secondary amine and phenol functionality may react with the epoxy resin and subsequently cure through an imidazole catalyst. Imidazole catalysts promote both the epoxy/phenol reaction and the anionic maleimide crosslinking. The formation of a 1 2 BMI/aminophenol adduct, as in Fig. 20, is claimed in a patent (63). The hydroxy terminated BMI/aminophenol adduct is an advantageous curing agent for epoxy resins when high temperature performance is desired. 

As in the cyanate/epoxide compositions, polysulfone is used as an additive in cyanate/epoxide/maleimide systems. As an example, a composition for carbon-fiber composites should be mentioned. It contains BPA/DC-BMI prepolymer, epoxide resin and polyethersulfone [111-113] Zn acetate and dicumyl peroxide are added. Polyethersulfone powder was added to the three-component system with 4,4 -diamino-diphenylmethane-based tetraepoxide as one of the epoxy resins used [114]. 

A special case is the binding of maleimides onto Tr resins (151) [260]. The latter were used efficiently in Diels-Alder and [2 -1- 3]-heterodipolar additions [261]. By anchoring maleimide to a trityl chloride resin through its silver salt [260], Barrett and co-workers [261] were able, after performing a one-pot synthesis by combining the preformed free base of the amino ester, the aldehyde, the dehydrating agent, the Lewis acid and the base in the presence of the solid-supported maleimide, to obtain the desired cycloadduct product (157). In this way, they were able to produce a 120-member library (Scheme 32). 

The t-BOC protection group chemistry has been extended to other aqueous-base soluble polymers such as poly[styrene-co-N-(4-hydroxyphenyl)maleimide], ° poly(styrene-co-maleimide), poly(4-hydroxystyrene sulfone), and poly(4-hydroxy-a-methylstyrene) used in lithographic applications. Even novolac resins have been successfully protected with the t-BOC group,which has resulted in significant reduction of the DUV absorption of these resins. ... 

A DNS-based positive photoresist can be used for deep-UV exposures if the binder resin in the photoresist itself does not absorb. Since novolacs made fi-om the condensation of formaldehyde with pure p-cresol (instead of commercial cresol mixtures) are found to have very transparent windows at about 250 nm, a DNS/p-cresol novolac-based photoresist gives a positive image after deep-UV exposure and development with aqueous base. A copolymer of styrene and maleimide is also used in place of novolac as a binder for DNS-based deep-UV positive resists. 

The majority of base materials for circuit boards are combinations of a copper foil with a laminate, where the laminate itself consists of a carrier material and a resin. Thus properties of the base material such as mechanical strength, dimensional stability, and processi-bility are determined primarily by the carrier material. On the other hand, the resin materials are responsible for the thermomechanical and electrical properties as well as for its resistance against chemicals and moisture. Frequently used carrier materials are based on glass and carbon fibers, papers, and polyamide, whereas the majority of the laminating resins are thermosets such as epoxies, phenolics, cyanates, bismaleimide triazine (BT) resins, maleimides, and various combinations of these [13]. 

Electrons accelerated to 3-10 MeV are traveling at about 99% the speed of light. Approximately 50% of the beam energy is lost in hard collisions that remove electrons from host atoms and thereby produce ionized species. As a result of hard collisions, polymerization can occur by free-radical or ionic mechanisms. Materials that proceed via free-radical polymerization include acrylic/methacrylic systems, maleic and fumaric polyester resins, maleimides, and thiole-ene systems. Of these systems, resins based on acrylic and methacrylic ftinctionalities have been studied the most (116). The other major material system to be studied is that of epoxy polymerized via a cationic mechanism, which requires a diaryliodonium or triaryliodonium salt catalyst. 

Oligomers end-capped with maleimide rings, which are known as bismaleimide (BMI) resins, exhibit thermal stability intermediate between epoxies and poly-imides. BMI systems are mainly used to fabricate structural composites capable of sustaining temperatures up to 230°C. Specific versions, such as American Cyanamid FM 32 and Ciba-Geigy Kerimid 601 have been developed to prepare adhesive compositions. Fig. 17 displays a typical constitutive unit of various commercial BMI resins based on bismaleimide 38, prepared from maleic anhydride 37 and 4,4 -methylenebisbenzeneamine (MDA) 34. 

A similar approach to estimating the composition of phase-separated regions and their content, based on the above-mentioned Fox equation, was later used for IPNs based on PU and maleimide-terminated PU [97], PU-epoxide-episulfide resin [102], and other systems. The results were not satisfactory, which can be explained by the approximate nature of the Fox equation (presently, there are a great number of equations connecting the glass transition temperature in compatible blends with transition temperatures of components). 

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