Amines weight control

The protected amine and primary amine ended polymers show the good molecular weight control and narrow MWD s one expects of anionic polymers. In addition, the hydrolysis of the protecting group does not disrupt polydiene backbones. Such procedures are also gel free. The polymers formed exhibit functionalities approaching the theoretical values, especially for low molecular weight (high amine content) polymers (Table VI), (14, 2). 

Figure 5.24. The Vogtle approach to yield low molecular weight amines via controlled sequential synthesis.

Interfacial polymerization will tolerate the presence of impurities in the reactants that simply dilute the material and thereby produce nonequivalence of reactants. These diluents might be water or inert contaminants in the acid chloride. Reactive monofunctional species are harmful in either phase. To maximize molecular weight, it is essential to use high purity monomers. Molecular weight control can be achieved, if desired, with appropriate use of monofunctional reagents. Examples of impurities interfering with the interfacial polyamidation of MPDI are half hydrolyzed acid chloride, monoamide, partially oxidized amines, and reactive surfactants. 

REAL LIFE MEDICINE 21-1 Physiologically Active Amines and Weight Control... 

Amines are not the only agents that are being investigated for their potential in weight control. For example, the completely nondigestible fat olestra contains no nitrogens, and its development is based on the finding... 

Catalytic activity can be considerably increased if the magnesium chloride is first combined with a suitable Lewis base, such as an ester, acid, alcohol, or amine, before reaction with an excess of titanium tetrachloride and subsequent activation with triethyl aluminum. Polyethylene produced with these catalysts has a lower molecular weight than that from the titanium trichloride catalysts mentioned earlier and less hydrogen is needed for molecular weight control. 

Amines have odd numbered molecular weights which helps identify them by mass spectrometry Fragmentation tends to be controlled by the formation of a nitrogen stabilized cation... 

Polymerization. The polymerization of aziridines takes place ia the presence of catalytic amounts of acid at elevated temperatures. The molecular weight can be controlled by the monomer—catalyst ratio, the addition of amines as stoppers, or the use of bifimctional initiators. In order to prevent a vigorous reaction, the heat Hberated during the highly exothermic polymerization must be removed by various measures, ie, suitable dilution, controlled metering of the aziridine component, or external cooling after the reaction has started. 

Lubrication oil additives represent another important market segment for maleic anhydride derivatives. The molecular stmctures of importance are adducts of polyalkenyl succinic anhydrides (see Lubrication and lubricants). These materials act as dispersants and corrosion inhibitors (see Dispersants Corrosion and corrosion control). One particularly important polyalkenyl succinic anhydride molecule in this market is polyisobutylene succinic anhydride (PIBSA) where the polyisobutylene group has a molecular weight of 900 to 1500. Other polyalkenes are also used. Polyalkenyl succinic anhydride is further derivatized with various amines to produce both dispersants and corrosion inhibitors. Another type of dispersant is a polyester produced from a polyalkenyl succinic anhydride and pentaerythritol [115-77-5]. 

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). 

In solution-based polymerisation, use of the initiating anionic species allows control over the trans /cis microstmcture of the diene portion of the copolymer. In solution SBR, the alkyUithium catalyst allows the 1,2 content to be changed with certain modifying agents such as ethers or amines. The use of anionic initiators to control the molecular weight, molecular weight distribution, and the microstmcture of the copolymer has been reviewed (15). 

The polymerization rate is controlled by the slowest process. Thus it is important to establish the rate controlling steps. The starting material for the (SPP) can be the dry nylonsalt Z 4) but mostly a low or middle molecular weight polymer is used. The polyamide-salts have the disadvantage of high amine losses 3 4). 

A new approach of controlling NCA polymerization was reported by the Cheng group in 2007 [22]. hr a screen of amine initiators for the polymerization of Bn-Glu NCA, they found that hexamethyldisilazane (HMDS) showed remarkable control of polymerizations and led to formation of PBLG with excellent chain length control, with less than 22% deviation from the expected molecular weights, and narrow molecular weight distributions < 1.2) (Scheme 13). The NCA polymer-... 

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