Solution polyaddition

The extent of the latter reaction is a function not only of the nature and concentration of the catalyst used, but also of the temperature at which the melt (or solution) polyaddition reaction is carried out. Extensive branching can lead even at low conversions of the phenolic OH group to gelation. It is, therefore, of considerable practical importance to determine the extent of branching in such systems. Earlier NMR studies (l)on conventional epoxide resins (M = 1500-4000) has shown thaT the branching points per molecule varies between 0.09 to 0.6. 

Solution polyaddition To the correct proportions of BADGE and BPA sufficient diglyme was added to prepare a 50 (w/w) diglyme solution. The solution was brought to the desired temperature, a reference sample taken, and the catalyst solution in diglyme injected to start the reaction. Samples were taken at regular intervals. 

Polyaddition reactions based on isocyanate-terminated poly(ethylene glycol)s and subsequent block copolymerization with styrene monomer were utilized for the impregnation of wood [54]. Hazer [55] prepared block copolymers containing poly(ethylene adipate) and po-ly(peroxy carbamate) by an addition of the respective isocyanate-terminated prepolymers to polyazoesters. By both bulk and solution polymerization and subsequent thermal polymerization in the presence of a vinyl monomer, multiblock copolymers could be formed. 

Microgels can not only be synthesized by polymerization but also by polycondensation or polyaddition [350]. In an early work on crosslinking of single linear macromolecules, it could be shown that if a crosslinking agent, such as terephthal dialdehyde, was added to a very dilute solution of a linear polymer such as polyvinyl alcohol, almost exclusively a intramolecular crosslinking of the individual macromolecules took place [351]. 

Next we consider the dispersion polymerization by polyaddition. In a typical method to prepare polyimide particles, polyamic acid solution is first obtained by coupling of pyromellitic dianhydride and oxy-dianiline, and then by heating the solution. The condensation reaction on heating causes crystallization of polyimide in a spherical form (Fig. 11.2.5, left) (33). However, on the contrary to this conventional method, polyamic acid microspheres could be obtained by dispersion polymerization if an appropriate medium is chosen (34). When a solvent that has a solubility parameter around 17 Mpa is used, submicrometer-sized monodisperse polyamic acid parti-... 

Many reactions familiar to organic chemists may be utilized to carry out step polymerizations. Some examples are given in Table 2.2 for polycondensation and in Table 2.3 for polyaddition reactions. These reactions can proceed reversibly or irreversibly. Those involving carbonyls are the most commonly employed for the synthesis of a large number of commercial linear polymers. Chemistries used for polymer network synthesis will be presented in a different way, based on the type of polymer formed (Tables 2.2 and 2.3). Several different conditions may be chosen for the polymerization in solution, in a dispersed phase, or in bulk. For thermosetting polymers the last is generally preferred. 

Aromatic polyimides are most useful super engineering plastics which exhibit excellent thermal, electrical, and mechanical properties, and have been used widely in aerospace, electronics, and other industries over the past three decades [ 1 -4]. Aromatic polyimides are generally prepared through a two-step procedure by the ring-opening polyaddition of aromatic diamines to aromatic tet-racarboxylic dianhydrides in NMP (or DMAc) solution giving soluble polyamic acids, followed by thermal cyclodehydration (Eq. 1) [1-5]. 

Forasmuch as 1,7- and 1,5-divinylcyclohexasiloxanes, used in polyaddition, represent mixtures of cis- and tram-isomers of the approximate 52 48 ratio, synthesized copolymers are atactic. Reprecipitation of copolymers from toluene solution by methyl alcohol has given viscous or solid (with regard to the value of flexible junction) transparent products with T sPec=0.09-0.29, well soluble in different organic solvents. It is found that at short length of dimethylsiloxane unit (n < 4), copolymer yields are slightly decreased that may be explained by partial proceeding of hydride polyaddition by intramolecular cyclization mechanism (see Tables 3 and 4). 

Hydride polyaddition of divinyl-containing compounds was carried out for various lengths of a,co-dihydridedimethylsiloxanes. The reaction run was searched by a decrease of active =Si-H groups concentration. It was found that for rhodium acetylacetonatedicarbonyl as a catalyst, copolymers soluble in organic solvents were obtained, which were structured after some time. This may be explained by the fact that in spite of polymers re-precipitated from toluene solution by methyl alcohol, rhodium catalyst remains in polymeric systems, which decompose and induce structuring (cross-linking) of copolymers. 

The polymers were synthesized by hydride polyaddition with 0.01N platinum-hydrochloric acid-tetrahydrofuran solution as the catalyst. The catalyst concentration equaled 5xl0 6 g per 1 mole of vinyl component in the temperature range of 60 - 150°C. It has been found that the reaction pro-ceeding at high temperatures displays formation of branched structures. The effect of initial mo-nomers structure on the formation rate of polymers, as well as on physical and chemical properties and structural features of synthesized polymers are traced. The reaction proceeds by the general scheme as follows [80] ... 

As the catalyst for polyaddition, 0.01 M solution of platinum hydrochloric acid in tetrahydrofuran was used. Polyaddition proceeds in argon at equimolar ratio of initial substances (1 1) in the absence of solvent and in the temperature range of 75 - 115°C. It is found that the above-mentioned con-ditions do not induce scission of the siloxane ring. As a consequence, hydride polyaddition under se-lected conditions proceeds in accordance with the scheme as follows [85 - 87] ... 

A series of Ji-conjugated organoboron polymers were successfully prepared by simple polyaddition between aromatic diynes and mesitylborane in a dry TTTF solution (Table 1). The polymerization preceeded smoothly at room temperature without catalyst to afford the corresponding polymers whose Mn were in the range of several thousands. 

FippioketoDe. To minimize tSoe hydrolysis of the lactrme, the sslta must be used in concentrated aqueous solution. The psirasitical polyaddition reaction (see eeotion VIII) is avoided - by addition... 

One of the methods for the synthesis of high molecular weight polyhydroxy ethers based on Bisphenol A is the base catalyzed polyaddition of the diglycidyl ether of Bisphenol A (BADGE) with Bisphenol A (BPA) in the melt or in solution (Scheme 1). 

In this paper we report experimental results on the kinetics of the polyaddition reaction in the melt and in solution (diglyme) using two different catalysts, namely tetrabutyl ammonium hydroxide (TBAH) and benzyl triethyl ammonium chloride (BTAC) at different temperatures. By simultaneous measurements of a, and in two cases we have also evaluated the critical branching parameters. 

Chemical Drying. Chemically drying paints contain binder components that react together on drying to form cross-linked macromolecules. These binder components have a relatively low molecular mass, so that their solutions can have a high solids content and a low viscosity. In some cases, solvent-free liquid paints are possible. Chemical drying can occur by polymerization, polyaddition, or polycondensation. 

Hydrophilic materials can be encapsulated with the inverse minianulsions by using interfacial polymerization such as polyaddition and polycondensation, radical, or anionic polymerization. Crespy et al. reported that silver nitrate was encapsulated and subsequently reduced to give silver nanoparticles inside the nanocapsules. The miniemulsions were prepared by anulsilying a solution of amines or alcohols in a polar solvent with cyclohexane as the nonpolar continuous phase. The addition of suitable hydrophobic diisocyanate or diisothiocyanate monomers to the continuous phase allows the polycondensation or the cross-linking reactions to occur at the interface of the droplets. By using different monomers, polyurea, polythiourea, or polyurethane nanocapsules can be formed. The waU thickness of the capsules can be directly tuned by the quantity of the reactants. The nature of the monomers and the continuous phase are the critical factors for the formation of the hollow capsules, which is explained by the interfacial properties of the systan. The resulting polymer nanocapsules could be subsequently dispersed in water. 

---