Polystyrene as an inert medium in the synthesis of the styrene/divinylbenzene/acrylonitrile copolymers

Abstract

Samples of styrene/divinylbenzene/acrylonitrile macroporous copolymers were prepared, using polystyrene as inert medium. The initial viscosity average molecular weight of the polystyrene samples were:Mv ,= 87000, 98000, 117000 and 218000. The polystyrene samples with the initial molecular weights Uv, = 87000 and Rv., = 117000 were reused as inert media, for many times, until they lost their capacity to produce permanent porosity of the copolymers. The macroporous copolymers were characterized by their permanent porosity and volume swelling. If a polystyrene sample is used for many times, the molecular weight of the polystyrene removed (extracted) is gradually diminished and therefore the permanent porosity of the macroporous copolymers decreases step by step. The reasons responsible for this behaviour are:during the copolymerization process a polystyrene with a smaller molecular weight is formed, -polystyrene parts of high molecular weights are included in the network structure of the macroporous co-The evidence for this was given by plotting the differential and integral molecular weight distribution curves polymers.for six samples of polystyrene.(mv) of PS is higher than 50 000 the copolymers formed possess a permanent porosity. Their characteristics (pore volume, pore radius) are dependent on the concentration and mv of PS introduced into the monomer mixture. Unlike the low molecular weight inert media during the copolymerization process, PS undergoes alterations of its polydispersion. This is reflected first of all by the decrease of the molecular weight (Hv) of extracted PS4.5).For the purpose ofestablishing the conditions to reuse extracted PS as diluent in the synthesis of the permanent porous copolymers, the causes that led to the molecular weight decrease of extracted PS in correlation with the molecular weight of initial PS (=",,) were studied. Experimental PartFreshly distilled styrene, technical divinylbenzene (57% by weight divinylbenzene) and acrylonitrile were used as monomers. The copolymerization reaction was initiated by benzoyl peroxide (1.0% by weight referred

PAN composite membrane with different solvent affinities controlled by surface modification methods

“…Two main reactions would be possible to occur by the interaction between the PAN composite membrane and EDA in gas phase: the reaction with nitrile groups with the formation of either amidine cycles or amide groups, which usually needs a temperature higher than 100 °C,15–17 and the formation of ammonium salts between the carboxylic groups, present on the surface as a consequence of the oxygen plasma treatment, and the primary amine groups of EDA. Figure 1 shows the FTIR spectra of the PAN composite membrane before and after the reaction with EDA in gas phase.…”

“…To achieve this objective, PAN membrane was first modified by a chemical treatment with ethylenediamine (EDA). It is known that nitrile groups react with EDA, in certain conditions, generating either imidazoline cycles,15 in the absence of water, or 2‐aminoethylacrylamide groups, in the presence of water 16, 17. On the other hand, the composite PAN membrane used in this study has been previously activated by oxygen plasma treatment.…”

Ion‐exchange resins. III. Functionalization–morphology correlations in the synthesis of some macroporous, strong basic anion exchangers and uranium‐sorption properties evaluation

“…Tipically, BPO (1 wt % relative to monomers) was added to monomers and then the corresponding amount of 2EH to form the organic phase. The organic phase was then added in a volume ratio of 1/2.5 to the aqueous phase that contained 0.4 wt % ammonium salt of S–maleic acid copolymer, 0.1 wt % food grade gelatine and 1 wt % NaCl,45 prepared in a four‐necked reaction reactor (1000 mL) fitted with a mechanical stirrer, condenser, and thermometer. The stirrer speed was kept around 400 rpm to obtain at least 90 wt % beads with the diameter within the range 90–200 μm.…”

“…After the first systematic studies on styrene–divinylbenzene (S–DVB) networks having a permanent porous structure in the dry state,1–9 the correlation between the synthesis conditions and the copolymer morphology has been extensively investigated 10–23. Their uses are connected with a large variety of separation processes having a great interest in industry and science.…”