Oligomers, amine terminated

Detailed information on the copolymerization of cyclic trifluoropropylmethyl-siloxane trimer and octamethylcyclotetrasiloxane is also very limited in the open literature26 27 . Recently, preparation of various amine terminated (dimethyl-tri-fluoropropyl,methyl)siloxane oligomers with varying molecular weights and backbone compositions has been reported 69115 ll7). Table 11 shows various properties of the oligomers produced as a function of composition. These types of modification play very important roles in determining the solubility characteristics and hence the compatibility of resultant polysiloxanes with other conventional organic monomers... 

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

More recently, St. Clair and co-workers176) reported the use of aromatic amine terminated polydimethylsiloxane oligomers of varying molecular weights in an effort to optimize the properties of LARC-13 polyimides. They observed the formation of two phase morphologies with low (—119 to —113 °C) and high (293 to 318 °C) temperature Tg s due to siloxane and polyimide phases respectively. The copolymers were reported to have improved adhesive strengths and better thermal stabilities due to the incorporation of siloxanes. 

ABA type poly(hydroxyethyl methacrylate) (HEMA) and PDMS copolymers were synthesized by the coupling reactions of preformed a,co-isocyanate terminated PDMS oligomers and amine-terminated HEMA macromonomers312). Polymerization reactions were conducted in DMF solution at 0 °C. Products were purified by precipitation in diethyl ether to remove unreacted PDMS oligomers. After dissolving in DMF/toluene mixture, copolymers were reprecipitated in methanol/water mixture to remove unreacted HEMA oligomers. Microphase separated structures were observed under transmission electron microscope, using osmium tetroxide stained thin copolymer films. 

Table 1. Characteristics of amine terminated aryl ether oligomers ...

Table 9. Aromatic amine terminated thermally labile oligomers ...

Arylene ether/imide block copolymers were prepared as depicted in Eq. (15) from the reaction of amine terminated arylene ether oligomers with theoretical molecular weights of 3110 and 6545g/mol with anhydride terminated amide... 

The key to acetylene terminated polyimides is the availability of the end-capper which carries the acetylene group. Hergenrother (130) published a series of ATI resins based on 4-ethynylphthalic anhydride as endcapping agent. This approach first requires the synthesis of an amine-terminated amide acid prepolymer, by reacting 1 mole of tetracarboxylic dianhydride with 2 moles of diamine, which subsequently is endcapped with 4-ethynylphthalic anhydride. The imide oligomer is finally obtained via chemical cyclodehydration. The properties of the ATI resin prepared via this route are not too different from those prepared from 3-ethynylaniline as an endcapper. When l,3-bis(3-aminophenox)benzene was used as diamine, the prepolymer is completely soluble in DMAc or NMP at room temperature, whereas 4,4 -methylene dianiline and 4,4 -oxydianiline based ATIs were only partially soluble. The chemical structure of ATIs based on 4-ethynylphthalic anhydride endcapper is shown in Fig. 45. 

Segmented copolymers with polyimides were produced by Keohan [43] and also by Smith [44], who also utilized the same coupling reaction with other amino-terminated engineering thermoplastics (ETP) to produce perfectly alternating block sequences. The generalized scheme for the reaction of the anhydride functional oligomer with amine-terminated polyimides or other ETP s is provided in Scheme 7. 

Chemical functionalization of the thermoplastics was found to improve toughness without such detractions. High-molecular-weight resins based on amine-terminated PES oligomers or chain extension of bismaleimide resin with the same amine-terminated PES were found to have improved fracture resistance and reduced thermal shrinkage.14 Also a mechanism was found to toughen cyanate esters by incorporating epoxy resins, which can react with the ester.15... 

Synthesis of piperazine-terminated oligomers as prepolymers for interfacial membrane formation was also examined.46 48 Excess piperazine was reacted with di- and triacyl chlorides in an inert solvent such as 1,2-dichloroethane. The resulting amine-terminated polyamide oligomers had low solubility in the solvent system and precipitated. This served to limit the degree of polymerization of the oligomer. Even so, a portion of the product was insoluble in water and was filtered out during preparation of the aqueous oligomeric amine solution for the interfacial reaction step. 

Epoxy toughening additives initially were based on rubbery inclusions or functionalized oligomers (carboxy or amine terminated butadiene/ acrylonitrile copolymers). More recently, impact modifiers (core-shell type) similar to that commonly employed with PVC have been proposed. For composites, tougher epoxy matrix candidates... 

A very similar equilibration was conducted as shown in Scheme 6 for the synthesis of secondary amine terminated siloxane oligomers. The amine terminated disiloxane here is a secondary... 

The Effect of Amine Structure In order to evaluate the effects of eunine functionality and substitution on the crosslinking reaction/ several amine terminated urethane oligomers were synthesized by the same procedure as used in the synthesis of the LPUR. The oligomers were prepared in Urethane Grade MEX. These amines were evaluated with the allyl terminated unsaturated polyester as the unsaturation source. The composition and the properties of the oligomers are shown in Table IV. 

The different grafting of monofunctional oligomers (aliphatic and aromatic amine, or hydroxyl functionalities) was investigated at different temperatures (180 °C and at 200 °C). The amine-terminated PMMA led to high yields in comparison with hydroxyl-terminated PMMA, whereas the grafting efficiency was very low [25]. 

The copolymer synthesis was carried out in a three neck round bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer and a condenser with drying tube. The stoichiometry was offset by using an excess of the polyimide oligomer. In every case, the calculated was 40,000 g/mole. The polyimide oligomer was dissolved in chlorobenzene and heated to -125 C. The amine terminated oligomer was added slowly and rinsed with chlorobenzene to bring the final reaction solids content to 15 percent. The reaction was stirred at -125 C for 2 hours. The solution was cooled to ambient temperatures and cast into films. The films were heated slowly in a vacuum oven and dried for at least 3 hours at 250°C. 

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