Synthesis of poly(acrylamide‐co‐divinylbenzene) microspheres by precipitation polymerization

Abstract

The synthesis and application of polymeric microspheres are of great importance from both academic and industrial points of view. As polymeric microspheres have been used in wider fields of conventional 1 and more sophisticated 2-6 areas, the development of a new process to prepare such materials has received much attention. Polymer microspheres of a particular size and uniformity are generally obtained with one of the heterogeneous polymerizations, including suspension, emulsion, dispersion, seeded, and precipitation polymerizations. Moreover, each polymerization is branched to several subsidiary methods, such as macroemulsion, miniemulsion, microemulsion, and soap-free emulsion polymerizations.Fully crosslinked monodisperse polymer microspheres have unique applications because of their superior strength, thermal and solvent resistance, and antislip properties.7 However, the synthesis of such microspheres is limited to a few techniques, such as seeded polymerization, [8][9][10][11] Shirasu porous glass (SPG) membrane emulsification followed by postpolymerization, 12,13 and precipitation polymerization.14 Precipitation polymerization, in particular, has advantages over the other techniques because crosslinked microspheres can be readily prepared in a single process without any auxiliary apparatus to make the size distribution of the particles narrow. Therefore, homoand copolymerization systems have been thoroughly investigated, including poly(divinylbenzene), 15 poly (methacrylic acid-co-polyethylene oxide methyl ether methacrylate), 16 poly(methacrylate-co-divinylbenzene), 17 poly(chloromethylstyrene-co-divinylbenzene), 18 poly(divinylbenzene-co-maleic anhydride) 19 , poly(methyl methacrylate-co-divinylbenzene)[poly(MMA-co-DVB)], [20][21][22] and poly(styrene-co-divinylbenzene) [poly(St-co-DVB)]. 23In addition, mechanistic studies to elucidate the formation of stable microspheres in the absence of any stabilizer have been reported 24,25 in which the absorption of oligomeric species onto the nuclei and the high degree of crosslinking are the primary reasons for the formation and stable growth of the microspheres.Several examples of the copolymerization of the partially water-soluble monomer acrylamide (AAm) and oil-soluble monomers such as methacrylic acid 26 and styrene 27,28 have been recently reported with precipitation polymerization, 26 inverse microemulsion polymerization, 27 and water/oil/water emulsion by SPG membrane emulsification and subsequent suspension polymerization. 28In our previous studies, poly(St-co-DVB) and poly (MMA-co-DVB) microspheres containing various concentrations of divinylbenzene (DVB), from 5 to 75 mol %, were synthesized by precipitation polymerization, and their unexpected thermal properties, superior to those of crosslinked polymers prepared by emulsion and

A One‐Pot Approach to Novel Cross‐Linked Polyphosphazene Microspheres with Active Amino Groups

“…For the present experiment, when the concentration of HCCP was 1 mg · mL −1 [Figure 4(a)], severe coagulation was observed, which could be attributed to the lack of elastic strength against the intercollision between the particles during the precipitation polymerization 30. The formation and stable growth of the microspheres were strongly dependent on the absorption of oligomeric species onto the nuclei and the high degree of cross‐linking 31. The high degree of cross‐linking within the particles is important to coagulum‐free configuration, because the improved hardness and resilience of the individual particles can prevent fusion or coagulation between the particles 30.…”

Precipitation Polymerization in Ethanol and Ethanol/Water to Prepare Uniform Microspheres of Poly(TMPTA‐styrene)

“…[18,21] The use of ethanol was believed to be the key point for these achievements, because it would have reduced the solubility of the oligomers, thereby accelerating particle formation. With this in mind, a set of experiments were performed using a mixture of ethanol and water as the polymerization medium, while keeping the other experimental conditions unchanged.…”

“…The monomer conversions in Table 1 were quite high when compared to those in previous reports on the precipitation polymerization of DVB and DVB-St, where 24 h of polymerization time was needed to reach the final monomer conversion, which increased at a quite slow pace. [18,21] To find out how the monomer conversion evolved in the present system, three runs were carried out with a varied TMPTA/St ratio while keeping the monomer concentration constant at 2 vol.-% and the initiator concentration at 2 wt.-%. Results are plotted in Figure 2, which indicate a rapid initial polymerization rate, and that the final conversion is reached within 2 h for the runs with 20 and 50 wt.-% of TMPTA.…”

“…The polymerization time lasted 24 h at 70 8C, and monomer conversions were relatively low, with the highest at about 70%. [14,17,21,22] Stöver et al have also reported that monomer conversion is enhanced with a polar monomer. The particle yield was increased from 43% to 90% with EGDMA (ethylene glycol dimethacrylate) increased from 10% to 90% in EGDMA-DVB copolymerization.…”

“…[18] Choe et al have also conducted the precipitation polymerization of DVB with other monomers. [19][20][21] In all these reports, the monomer concentration was kept at 2 wt.-% relative to acetonitrile. The polymerization time lasted 24 h at 70 8C, and monomer conversions were relatively low, with the highest at about 70%.…”