Grafting percent

Cinchonidine displays a tertiary amine, an aromatic amine and a free hydroxyl functionality. Direct hydrosilylation with unprotected cinchonidine (derivatized with a double bond for hydrosilylation), led to a cross-linked product. Thus, hydrosilylation was performed on PHMS with the trimethylsilyl derivative 1 (Fig. 10), in the presence of (EtjS)jPtClj as catalyst (0.05%), for 6h at 80°C in toluene. The hydroxyl group was deprotected with methanol at 65°C during 120 h. Size Exclusion Chromatography showed that the polysiloxane backbone was not degraded. A maximal grafting percent of 15% could be obtained, relative to the SiH units. 

Grafting percent (Gp %) and grafting efficiency (GE %) were calculated... 

Grafting percent (Gp), and grafting efficiency (Ge) were obtained by the gravimetric method according to the following definitions ... 

Figure 1. Grafting Percent and grafting efficeiency of NVP onto PLA film vs. Irradiation time. 

Two parameters such as percentage of grafting (%G) and grafting efficiency are usually determined as functions of different variables that influence graft copolymerization. Percent grafting is usually determined from the increase in weight of the backbone polymer after grafting after complete removal of the homopolymer. It is expressed as follows ... 

This is the same order of the solubility of the monomer in water. The increase in acrylonitrile concentration increases the percent grafting and grafting efficiency. 

Photo-induced grafting onto wood cellulose with several vinyl monomers using phenyl acetophenone and benzophenone derivatives as photosensitizers has been reported [72]. A fast increase in grafting was observed for short irradiation times, whereas longer ones resulted in a decreased percent grafting. 

Figure 1 Effect of monomer concentration on the total conversion percent and grafting efficiency. LR 30 I, acid concentration l%, initiator concentration 0. l%, grafting time 1 h, and reaction temperature 27°C — = total conversion (%) O—O = grafting efficiency (%).

The effect of acid concentration on the rate of grafting has been studied. It is clear that increasing the acid concentration from 0.5% to 1.0% increases not only the total monomer conversion percent from 60.1% to 61.5%, but also the grafting efficiency from 58.0% to 59.6%. This... 

Figure 3 Effect of residual lignin percent in the pulp on total conversion percent and graft yield percent. LR 40 1, reaction time 1 h, reaction temperature 27°C, monomer concentration 1 mL/g pulp, initiator concentration 1%, and acid conversion 1% — = total conversion (%), O—O = graft yield (%).

Wood pulp and cotton linters were partially acetylated to different acetyl contents ranging from approximately 6%-13% (0.23-0.54 degree of substitution [D.S.]). The increase of the DS of partially actylated cotton linters from 0.26 to 0.56 causes the percent graft of partially acetylated cotton linters to decrease slightly from 0.93% to 0.6%. In the case of wood pulp, the effect is somewhat different—the percent graft increases with an increasing DS until about 0.48, then the percent graft decreases. 

Percent of graft copolymer Stress at 50% elongation (N/mm) Stress at 100% elongation (N/mm) Stress at 130% elongation (N/mm) Tensile strength (N/mm ) Elongation at break (%)... 

Grafted Davisil Expected Loading (mmol N/g) Experimental Results " (mmol N/g) Error (mmol N/g) Percent Error... 

In our own research, the functional termination of the living siloxanolate with a chlorosilane functional methacrylate leading to siloxane macromonomers with number average molecular weights from 1000 to 20,000 g/mole has been emphasized. Methacrylic and styrenic monomers were then copolymerized with these macromonomers to produce graft copolymers where the styrenic or acrylic monomers comprise the backbone, and the siloxane chains are pendant as grafts as depicted in Scheme 1. Copolymers were prepared with siloxane contents from 5 to 50 weight percent. 

Grafting on the resin was achieved via a nucleophilic substitution of the benzylic chlorine by the deprotonated OH-linker of 52 (Scheme 29) by using a mixture of KO Bu, 18-crown-6 and CsBr. Determining the nitrogen content of solid phase samples by elemental analyses was accomplished, to verify the functionalization of the polymer. This enables calculation of the degree of functionalization. Usually, an occupancy of more than 20 percent of the theoretical sites was achieved. Saponification of the functionalized Merrifield resin P-52 leads to the monoanionic NJ, 0 functionalized solid phase. Subsequent reaction with [ReBrtCOlsJ afforded the polymer mounted tricarbonyl rhenium complex P-52-Re (Scheme 29). 

Moreover, alcohol functionalities have been introduced into the polynor-bornene (PNB) backbone by copolymerization of norbornene with a few percent of 5-acetate norbornene and subsequent acetate reduction. After transformation of the pendant hydroxyl functions into diethyl aluminum alkoxides, sCL has been ring opening polymerized (Scheme 31). Owing to the controlled/ liv-ing character of both polymerization processes the isolated poly(NB- -CL) graft copolymers were characterized by well-defined composition, controlled molecular weight and branching density, and narrow MWD (PDI=1.2-1.4) [92]. 

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