Polystyrene freeze drying

Polystyrene was prepared by the anionic polymerisation of styrene in toluene plus THF mixtures (4 1 volume ratio) using n-butyl lithium as initiator. After removing a sample for analysis at this stage, the remainder of the living polystyrene was reacted with a five molar excess of trichloromethylsilane for 15 min and then excess methanol introduced. The methoxy-terminated polystyrene was freeze-dried from dioxan. The method described here essentially follows the route proposed by Laible and Hamann (6). 

In this case some of the Sll silica was freeze-dried and degassed at 10-3 Torr and 150°C and then reacted with trichloromethylsilane in the vapour phase this replaced the surface hydroxyl groups by chloro groups. The particles were then redispersed (with the aid of ultrasonics) in a 4 1 volume ratio toluene THF solvent mixture. "Living" polystyrene (PS19), in a similar solvent mixture was then introduced and the grafting reaction allowed to proceed for 24 hr at room temperature. 

Amination (11) and solution carbonation (8) reactions were carried out as described previously. For solid-state carbonations, a benzene solution of poly(styryl)lithium was freeze-dried on the vacuum line followed by introduction of high-purity, gaseous carbon dioxide (Air Products, 99.99% pure). Analysis and characterization of polymeric amines (11) and carboxylic acids (8) were performed as described previously. Benzoyl derivatives of the aminated polystyrenes were prepared in toluene/pyridine (2/1. v/v) mixtures with benzoyl chloride (Aldrich, 99%). 

For radiolysis studies of the grafting solutions without cellulose, i.e. homopolymer runs, tubes were either lightly stoppered or sealed off at 10-J Torr after three freeze-thaw cycles. For the molecular weight determinations on the homopolymers, oligomer solution was poured into excess methanol, the precipitated polystyrene collected, dried and analysed by g.p.c. on a Waters Associates Model ALG/GPS201 instrument. 

Polyallylamine (Mw = 70 000 g/mol) and polystyrene sulfonate (M, = 70 000 g/mol) were obtained from Aldrich. PAH was used as received, while PSS was purified from low molecular weight impurities by dialysis (Polyether-sulfone membranes, MW cut off 10 000 g/mol, Millipore) against ultra pure water and freeze dried. All water used for preparing solutions or for dialysis was purified by a Purelab Plus UV/UF, Elga Lab Water system and had a resistivity smaller than 0.055 xS/cm and a total organic content between 2 and 12 ppb (parts per billion). 

Labelled polystyrene-14C (PS-14C) was the adsorbate. Two batches were prepared by an identical procedure with only one of them containing radioactive 14C. The labelled polymer was used for the adsorption measurements, whereas the unlabelled polymer was used for the determination of the solution properties. The polystyrene was prepared by emulsion polymerization of redistilled styrene. In order to remove unreacted monomer the polystyrene was freeze-dried from benzene solution. 

The functionalisation by thiols was performed as follows Small cubes of (vinyl)polystyrene polyHIPE [3.00 mmol C=C/g (1 g, 3 mmol C=C)] were impregnated with toluene by freeze-drying under vacuum and suspended in toluene (20 mL). The thiol (8 mmol), AIBN (5 mg, l%mol. / C=C) were then added. The suspension was heated at 70°C for 48 h. The polymer was filtered off, extracted with acetone overnight on a Soxlet apparatus and dried in vaccum at 60°C, overnight. 

After establishing the feasibility of the method , we have recently applied it to monodisperse polystyrene in good and poor so1ventsusing carbazole as the donor and anthracene as the acceptor. With these labels R = 2.75 nm. The ratio of anthracene and carbazole emission intensities, in the freeze-dried sample... 

Figure 2. Ratio of anthracene and carbazole emission intensities from freeze-dried mixtures of monodisperse polystyrene (M - 410,000) carrying 0.0092 moles/kg of the labels, relative to this ratio in films cast from solutions of a mixture of these polymers. Excitation at the carbazole absorption peak at 294 nm. Original solution in benzene dioxane (D) and cyclohexane (0). Arrows indicate l/iq] in the various solvents.

Studies on the dilute solution behavior of sulfonated ionomers have shown these polymers to exhibit unusual viscosity behavior in solvents of low polarity. These results have been interpreted as arising from strong ion pair associations in low polarity diluents. Solvents of higher polarity, such as dimethyl sulfoxide and dimethyl formamide induce classic polyelectrolyte behavior in sulfonate ionomers even at very low sulfonate levels. To a first approximation these two behaviors, ion pair interactions or polyelectrolyte behavior, are a consequence of solvent polarity. Intramolecular association of Lightly Sulfonated Polystyrene (S-PS) results in a reduced viscosity for the ionomer less than that of polystyrene precursor at low polymer levels. Inter-association enhances the reduced viscosity of the ionomer at higher polymer concentrations. Isolation of the intra- and inter-associated species of S-PS has been attempted (via freeze drying). A comparison of selected properties reveals significant differences for these two conformations. 

Preparation of Macromolecular Dioxolenium Salts. Living polystyrene prepared by the polymerization of styrene in THF with a-methylstyrene tetramer dianion reacted with a 2.1-molar amount of ethylene oxide for three hours at room temperature a 6.6-molar amount of adipoyl chloride was added, and the mixture was stirred for 20 horns a 20-molar amount of ethylenebromohydrin was added. This mixture was stirred for 44 hours. The bromoethylated polystyrene was precipitated in excess methanol and freeze-dried from benzene in a vacuum system. A 1-nitropropane solution of polystyrene dioxolenium salt was prepared by reaction of bromoethylated polystyrene with silver perchlorate in 1-nitropropane. Silver bromide was removed from the reaction mixture by filtration. Molecular weight of the product was measured by a vapor-pressure osmometer it was 1910 for living polystyrene and 5190 for the bromoethylated polystyrene. Bromine analysis of the bromoethylated polystyrene showed 67.9% of the calculated value. 

Scanning electron micrographs (SEMs) of (a,b) polyaniline (PANI) network in 25/25/25/25 polystyrene/polymethyl methacrylate/poly(vinylidene fluoride)/polyaniline (PS/PMMA/ PVDF/PANI) blend after extraction of all phases by dimethylformamide (DMF) followed by freeze drying, and (c,d,e) PANI network in 15/20/15/25/25 PS/PS-co-PMMA/PMMA/PVDF/ PANI blend after extraction of all phases by DMF followed by freeze drying. (Reproduced from Ravati, S., and Favis, B. D. 2010. Low percolation threshold conductive device derived from a five-component polymer blend. Polymer 51 3669-3684 with permission from Elsevier.)... 

Conductive polyaniline (PANI) formed the core of the five-component continuous system that also included high-density polyethylene (HOPE), polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(vinylidene fluoride) (PVDF) along with PS-co-PMMA copolymer. Figure 1.10 shows the SEM micrographs of PANI network in PS/PMMA/PVDF/PANI and PS/PS-co-PMMA/PMMA/PVDF/PANI blends after extraction of all phases by DMF followed by freeze drying. 

A rather specialized solid-state carbonation procedure can be used to carbonate PSLi and other living polymers with backbones which have glass transition temperatures significantly above room temperature. Thus, freeze-drying of benzene solutions of PSLi generates a porous solid which can be carbonated in the solid state to give minimal amounts of dimeric ketone products (1-2%). In addition, essentially quantitative yields of carboxylated polystyrene were obtained from freeze-dried solutions of PSLi that were complexed with 1-2 molar equivalents of TMEDA. No dimer was detected by SEC or TLC analyses. A freeze-dried sample of poly... 

Alp. 100 solution of polystyrene in carbon tetrachloride is freeze-dried. 

Needless to say, this sequenced freeze-drying operation could be repeated, say with a 2 p. 100 maltose solution in diethylamine, resulting in a triple intermingled network of three compounds polystyrene, dextran, and maltose and so on. 

Fig. 4.41 TEM micrographs of freeze dried polystyrene latex (A) used as a control for the experiment are three dimensional and show no deformation, whereas an air dried film forming latex (B) shows barely visible, flat regions that have no shadow. The same latex as in (B) after the freeze drying experiment has shadows (C), showing that the particles are three dimensional.

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