Homopolymer DADMAC

Polymerizations. Homopolymer DADMAC-Solution Polymerization. To a 1-L four-neck resin pot equipped with a mechanical stirrer, thermometer, condenser, purge tube, and heat regulating device were added 492 g of 55% aqueous DADMAC monomer. The pH was adjusted to 6.0 with dilute hydrochloric acid, heated to 50°C, and purged with nitrogen for 1 hr while stirring. Then, 0.05% Na4 EDTA (based on weight reaction mix) was added followed by 1.5 X 10 2 mol f-butyl-peroxypivalate/mol monomer. The temperature was maintained at 50°C 2°C for 18 hr, at which time the monomer conversion to polymer leveled off at 95%. The polymer was isolated via acetone precipitation. 

Homopolymer DADMAC-Emulsion Polymerization. The equipment setup outlined in the solution polymerization was used to prepare the emulsion polymer. To the resin pot 321.5 g benzene, 138.5 g of 72.2% aqueous DADMAC monomer, and 40 g of 20% aqueous sodium octyl phenoxyethoxy-2-ethanol sulfate were added. The mixture was stirred at 170-180 rpm with a paddle stirrer and heated to 50° 1°C. The suspension was purged with nitrogen gas for 1 hr. Then, 7 ppm Fe+2 (added as Fe(NH4)2(S04)3 6H20) were added, followed by 2 X 10"3 mol f-butylperoxypivalate/mol monomer. The reaction mixture was stirred for 20 hr at 50° 1°C under a nitrogen blanket. The polymer conversion after 20 hr was 90 2%. The product was isolated by adding the benzene emulsion to acetone, filtering the product, and drying. 

C-NMR spectroscopy has also been used to investigate the composition of DADMAC copolymers [38, 45-47]. Copolymers with acrylamide (AAM) have been extensively studied. Based on the chemical shifts in the 13C-NMR spectra of the homopolymers of DADMAC [17-19] and AAM [48-50], the copolymer spectra can be analyzed. Specifically from two likely chad structures (m/r) in PAAM and six different diad structures (r/m, c/t) in PDADMAC, eight different diad structures can be expected for the copolymers. A detailed NMR analysis has therefore been carried out in order to determine the copolymer compositions. The reactivity ratios obtained were found to be in good agreement with the results from other methods, such as potentiometric titration or elementary analysis, provided that the DADMAC in the copolymer was below approximately 70% [38]. 

The homopolymerization of DADMAC is possible in several organic solvents such as acetone, l-methyl-2-pyrrolidone, tetramethylurea, or dimethylform-amide. Various initiation methods including radical, ionic, or x-ray induced polymerization have been employed [19]. Since the monomer solubility is limited in these solvents, and the resulting homopolymer is soluble only in water, methanol and acidic acid, the polymerization in aqueous solutions are preferred. Polymerization in both homogeneous and heterogeneous systems have been studied and the kinetics and mechanisms were investigated in aqueous solution and in inverse-emulsion [6-16,52,53]. 

One objective of the copolymerization of DADMAC is to obtain higher polymer molar mass since the molar mass of the homopolymer is limited by a slow chain propagation (Table 4). Therefore, DADMAC has been copolymerized with various ionogenic and nonionic monomers of which acrylamide is the most common. A variation of the general properties such as water solubility or charge density also becomes possible by copolymerization. 

Homopolymers of DADMAC and copolymers of acrylamide and DADMAC are applied in the coagulation of fibers recycled from coated broke, a term used to describe a paper which cannot be sold for different reasons [ 176]. It is claimed that polymer solutions and water-in-oil emulsions containing DADMAC offer both superior performance and cost effectiveness compared to the traditional polymer additives used for this purpose [190,194]. 

Measurements. The monomer to polymer conversion for the DADMAC and AMBTAC homopolymers was measured by liquid chromatography. The DADMAC content in the precipitated DADMAC/acryl-amide copolymers was measured by Cl titration. 

A set of DADMAC homopolymers was synthesized via inverse emulsion. Concentrations of TAMAC ranging from 0 to 5.0 mol % (based on monomer concentration) were added to the monomer solutions before polymerization to induce branching. All polymerizations were initiated with the same concentration of a conventional free-radical catalyst. These samples were evaluated for their ability to dewater 100% activated sewage sludge. The filtration rate served as a measure of a sample s dewatering ability. 

Another series of DADMAC emulsion homopolymers was synthesized containing 0-0.5 mol % MBA. Data given in Table I indicate the same phenomenon of decreasing filtration rate with increasing MBA concentration as was observed for the series containing TAMAC. Hence, the enhanced dewaterability is independent of the type of branching agent employed. 

NMR measurements confirmed that five-member rings were formed in the copolymerization of DADMAC and AAM. A typical NMR spectrum is shovm in Figure 10. The assignments agree with those made by Lancaster for DADMAC homopolymers 24). Also, the compositions obtained by HPLC and NMR agreed reasonably well. However, the time required for an NMR analysis is about 20 h, so it is obviously not suitable for routine measurement of a series of samples. One HPLC measurement takes, by... 

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