Polymeric tertiary amines

Primary amine-containing polymeric particles are available from a number of manufacturers and have either aliphatic or aryl amine groups on their surface. Occasionally, a particle type may have secondary or tertiary amines present, but these should be avoided for covalent coupling, as primary amines typically give better reaction yields than secondary amines and tertiary amines are unreactive. 

Starch is the most widely used dry strength additive and is normally made in a cationic form by introducing a reactive monomeric or polymeric tertiary amine or quaternary ammonium derivative into the molecule. The most commonly used reagent for tertiary amino starch is 2-chloroethyldiethylammonium chloride, and for quaternary starch is 2,3-epoxypropyltrimethylammonium chloride (Figure 7.10). 

We were interested in the behaviour of polymeric catalysts in order to confirm that typical polymer effects may occur. Oxidative coupling of 2,6-disubstituted phenols, as developped by Hay (7), was chosen as a model reaction and the catalytic activities of coordination complexes of copper with several polymeric tertiary amines were compared with the activities of their low molecular weight analogs. The overall reaction scheme is presented in scheme 1. 

Some of these reactions are listed in Table 2.9, but they are not as clear as they are described in the table because catalysts that can also initiate a chain polymerization (tertiary amines, triphenylphosphine, imidazoles, chromates, etc see Sec 2.3.4) are practically always used. 

Sulfobetaines are typically prepared by alkylsulfonation of a monomeric or polymeric tertiary amine with strained sultones, usually 1,3-propanesultone or 1,4-butanesultone. An alternative route is the reaction of tertiary amines with a haloalkylsulfonate. Most of the early investigations on polymeric betaines relate to the sulfo derivatives 23a-e, 24, 25, and 26 listed in Scheme 5 [1-4,178]. 

This system has not been studied much recently [124, 125] save for one report by Cook [126], who found that, in the absence of amine, polymerization of a standard acrylate dental formulation proceeds to a limited extent. Polymerization is also extremely slow in the presence of primary amines or amines with no a-hydrogens. Tertiary aliphatic amines, however, accelerate the polymerization rate, as do ter-... 

A more difficult question is the initiation of formaldehyde with amines, notably tertiary amines. Kem et al. [15, 16] recently discussed the initiation of formaldehyde with Lewis bases. They favour initiation of formaldehyde polymerization by direct addition to the nucleophilic end of the amine... 

The authors studied the polymerization of formaldehyde with amines including tertiary amines at —78°C in various solvents (Table 1), and determined the conversion after 15 min reaction time. Tertiary amines are highly reactive initiators for formaldehyde polymerizations even at the level of 10 mole T per mole 1 of formaldehyde. The reactivity of the amine is related to its pXg value but also to the branching of the aliphatic side chains of the substituents on the nitrogen atom. Branched amines, especially when the branching is on the a-carbon atom as in the case of a tertiary butyl group, are less effective initiators than tertiary amines with n-alkyl chains. The pX a of the amine is not the essential feature for an efficient tertiary amine initiator, because pyridine was almost as effective as tri-n-butylamine but quinoline, with a similar pK g as pyridine, is almost inactive (Table 1). 

Isocyanates also react with primary and secondary amine compounds. Tertiary amines cannot react with isocyanates because they do not contain active hydrogen atoms, but they are powerful catalysts for many other isocyanate reactions. Diamines are frequently used as chain extenders and curing agents in PU manufacture. The addition of a diamine to the reaction mixture increases the overall reactivity during polymerization. The reaction between an isocyanate group and an amine results in the formation of a urea bond. The polyurea segments present in the finished PU serve to increase the potential for both covalent and hydrogen bond crosslinks within the polymer. 

In comparison to the previously discussed monomers, the polymerization of N-substituted aziridines is easier to control since the side reactions by proton transfer are eliminated because of the absence of primary and secondary amines. Nonetheless, termination by nucleophilic attack of the cationic propagating chain end into polymeric tertiary amines results in the formation of unreactive quaternary ammonium groups, that is, termination. As a result, the polymerization of N-substituted aziridines usually stops at limited conversion as was first demonstrated for A-methylaziridine by Jones [129]. Detailed evaluation of the polymerization kinetics as well as the evolution of molar mass during the polymerization revealed that termination mainly occurs via intramolecular backbiting... 

One of the most studied applications of SILMs is the selective separation of organic compounds. The first example was reported by Branco et al. [71], who studied the selective transport of 1,4-dioxane, 1-propanol, 1-butanol, cyclohexa-nol, cyclohexanone, morpholine, and methyhnorpholine as a model of seven-component mixture of representative organic compounds. For that, four ILs based on the l- -alkyl-3 methylimidazolium combined with the anion hexafluoro-phosphate or tetrafluoroborate, immobilized in different organic polymeric membranes, were used. The use of the IL [bmim+][PFg ] immobilized in a PVDF membrane allowed an extremely highly selective transport of secondary amines over tertiary amines (up to a 55 1 ratio). 

FIGURE 43.1 Three polymers based upon the [-CH2-CH2-N<] basic unit. Amines are shown in the uncharged state for clarity. (A) Linear PEL, (B) An example of a branched PEI. The polymerization permits 2° amines and one cyclization via a back biting reaction. The polymer is somewhat irregular (C) Third generation PAMAM dendrimer. All amines are tertiary amines (except for chain termini). 

Recently, benzophenone-based initiators with hydrogen donating amine moieties covalently attached via an alkyl spacer were introduced as photoinitiators for vinyl polymerization [101,126-130] (see 1, Table 10). Although also following the general scheme of lype II initiators, the initiation is a monomolecular reaction, as both reactive sites are at the same molecule. Hydrogen transfer is suspected to be an intramolecular reaction. The ionic derivatives (2 and 3) shown in Table 10 are used for polymerization in the aqueous phase [131-133]. With 4,4 -diphenoxybenzophenone (4 in Table 10) in conjunction with tertiary amines, polymerization rates that are by factor of 8 higher than for benzophenone were obtained [134]. 

Many perfluoroaUphatic ethers and tertiary amines have been prepared by electrochemical fluorination (1 6), direct fluorination using elemental fluorine (7—9), or, in a few cases, by fluorination using cobalt trifluoride (10). Examples of lower molecular weight materials are shown in Table 1. In addition to these, there are three commercial classes of perfluoropolyethers prepared by anionic polymerization of hexafluoropropene oxide [428-59-1] (11,12), photooxidation of hexafluoropropene [116-15-4] or tetrafluoroethene [116-14-3] (13,14), or by anionic ring-opening polymeriza tion of tetrafluorooxetane [765-63-9] followed by direct fluorination (15). 

Beryllium Hydride. BeryUium hydride [13597-97-2] is an amorphous, colorless, highly toxic polymeric soHd (H = 18.3%) that is stable to water but hydroly2ed by acid (8). It is insoluble in organic solvents but reacts with tertiary amines at 160°C to form stable adducts, eg, (R3N-BeH2 )2 (9). It is prepared by continuous thermal decomposition of a di-/-butylberylhum-ethyl ether complex in a boiling hydrocarbon (10). 

Commercially, polymeric MDI is trimerized duting the manufacture of rigid foam to provide improved thermal stabiUty and flammabiUty performance. Numerous catalysts are known to promote the reaction. Tertiary amines and alkaU salts of carboxyUc acids are among the most effective. The common step ia all catalyzed trimerizations is the activatioa of the C=N double boad of the isocyanate group. The example (18) highlights the alkoxide assisted formation of the cycHc dimer and the importance of the subsequent iatermediates. Similar oligomerization steps have beea described previously for other catalysts (61). 

Other Rea.ctions, The photolysis of ketenes results in carbenes. The polymeriza tion of ketenes has been reviewed (49). It can lead to polyesters and polyketones (50). The polymerization of higher ketenes results in polyacetals depending on catalysts and conditions. Catalysts such as sodium alkoxides (polyesters), aluminum tribromide (polyketones), and tertiary amines (polyacetals) are used. Polymers from R2C—C—O may be represented as foUows. 

Monofunctional, cyclohexylamine is used as a polyamide polymerization chain terminator to control polymer molecular weight. 3,3,5-Trimethylcyclohexylamines ate usehil fuel additives, corrosion inhibitors, and biocides (50). Dicyclohexylamine has direct uses as a solvent for cephalosporin antibiotic production, as a corrosion inhibitor, and as a fuel oil additive, in addition to serving as an organic intermediate. Cycloahphatic tertiary amines are used as urethane catalysts (72). Dimethylcyclohexylarnine (DMCHA) is marketed by Air Products as POLYCAT 8 for pour-in-place rigid insulating foam. Methyldicyclohexylamine is POLYCAT 12 used for flexible slabstock and molded foam. DM CHA is also sold as a fuel oil additive, which acts as an antioxidant. StericaHy hindered secondary cycloahphatic amines, specifically dicyclohexylamine, effectively catalyze polycarbonate polymerization (73). 

Cyanoacrylate adhesives cure by anionic polymerization. This reaction is catalyzed by weak bases (such as water), so the adhesives are generally stabilized by the inclusion of a weak acid in the formulation. While adhesion of cyanoacrylates to bare metals and many polymers is excellent, bonding to polyolefins requires a surface modifying primer. Solutions of chlorinated polyolefin oligomers, fran-sition metal complexes, and organic bases such as tertiary amines can greatly enhance cyanoacrylate adhesion to these surfaces [72]. The solvent is a critical component of these primers, as solvent swelling of the surface facilitates inter-... 

Possible impurities of the tertiary amine include primary and secondary amines. The presence of aniline slows the reaction, while the presence of A-methylaniline actually accelerates the polymerization [51]. As the secondary amine may be formed during polymerization (especially in the presence of water) reaction kinetics may be complicated. 

Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

However, as can also be seen in Fig. 11, primary and secondary amines do not perform very effectively as primers, compared to tertiary amines, even though they also contain long alkyl chains. It has been demonstrated that, instead of directly initiating ECA polymerization, primary and secondary amines first form aminocyanopropionate esters, 12, because proton transfer occurs after formation of the initial zwitterionic species, as shown in Eq. 7 [8,9]. 

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