Swelling steps

Two different methods have been used for the incorporation of the activating ogliomer (or monomer) in the seed particles. The first method involves the application of a small organic chemical, such as chloroundecane or dibutyl phthalate, which is incorporated into the particles in the first swelling step. In the second method, an ogliomer compound is formed by polymerization of monomers that are absorbed inside the seed particles. 

A new process, from Norway, has filled the size gap between emulsion and suspension polymerization techniques [7,8]. This novel polymerization method, the so-called swollen emulsion polymerization has been developed by Ugelstad for producing uniform polymeric particles in the size range of 2-100 /nm. This process comprises successive swelling steps and repolymerizations for increasing the particle size of seed polymer particles by keeping the monodispersity of the seed latex. 

The directions of the transitions between the various phases are indicated by the arrows, i.e., a transition from D to III is possible on application of dry heat. A transition from III to D is impossible unless a strong swelling agent like ammonia is used. A transition from III to I is possible by the application of water and heat or by a prolonged application of water at ambient conditions. The reverse transition is impossible without an intermediate swelling step. The transitions are usually not complete, especially in industries, and a wide range of products can be obtained as indicated by the phase diagram. The ammonia-cellulose complex and cellulose in can also be obtained from cellulose II. There is, however no reversion to cellulose I. 

Some peptide chemists believe that a shrink-swell step at this point will exercise the resin and help efficiency of synthesis, particularly when coupling is incomplete and recoupling will be used. To apply shrinking, wash the resin with MeOH (3 x 15 mL) to shrink the resin, then with CH2CI2 (3x) to swell the resin again before recoupling or the next coupling cycle. 

Fig. 2.40 Step height analysis of AFM height images of a thin polymer film prior to and after swelling (step heights of 19.0 and 21.3 nm were measured). Reproduced with permission from [31]. Copyright 2005. American Chemical Society...

In this method, the layered silicate is allowed to disperse within the liquid monomer or a monomer solution so that the polymer formation can occur between intercalated layers of the nanoclay. Polymerization can be initiated either by heat or radiation, by the utilization of a suitable initiator, or by an organic initiator or catalyst fixed through cation exchange inside the interlayer before the swelling step [32]. 

The organic solvent-free preparation method usually involves the rehydration of the copolymer in pure water and includes a film or bulk swelling step. In film swelling, copolymers are first dissolved in an organic solvent such as chloroform, and then a thin film is formed after evaporation of organic solvent. The subsequent addition of water or aqueous buffer solution hydrates the block copolymer to form vesicles. This method can also be applied for the... 

It has been reported that the thiocyanate method gives values of hydroperoxide content in oxidized polyolefins one order of magnitude below the true level because of the failure of the reagents to penetrate into the oxidized polymer films even after a prior swelling step. 

In a hypo-osmotic dilution (higher concentration in the internal phase), an increase up to a maximum value is observed, followed by a decrease, until equilibrium is reached. The first part of the curve corresponds to the swelling step, whereas the last part corresponds to the breakdown. 

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