Yang Wantai

SURFACE PHOTOGRAFTING POLYMERIZATION OF STYRENE ON LDPE FILM

ABSTRACT Styrene (St) was photografted onto LDPE substrates with different methods including a one-step method, pre-irradiation method, and pre-grafting method. Percent conversion (CP) and grafting efficiency (GE) of LDPE/St polymerization systems were measured by the gravimetric method. The results show that the one-step method is not very effective, no matter which photoinitiator (BP, BPO, Irgacure 651 and ITX) is used. The pre-irradiation technology, by which the dormant groups are introduced onto the substrates in advance, is favorable relatively. If the pre-grafting method is employed, AA is the most preferred one among the monomers examined (AA, MA and MAH). In addition, it is found that in the absence of photoinitiators and at lower temperatures (lower than 50°C), no grafted polymer is produced; but at a high temperature (e.g., 80°C), a remarkable amount of grafted polymer of St is formed (GE=44.9%). The phenomena indicate that St is prone to be grafted onto LDPE film by auto-initiation.

The investigation of terpolymerization of ethylene/propylene/ω-cl-α-vinyl monomers catalyzed by Cat.L-Pd catalyst

We investigated the terpolymerization of ethylene/propylene/ω-Cl-α-vinyl monomers to obtain polar terpolymers by non-metallocene catalyst Cat.L-Pd through coordination polymerization directly. The functional ω-Cl-α-vinyl monomer inserted into the polymeric molecules changed the properties of the obtained polymers. The optimum catalyst Cat.L-Pd and polymerization conditions were optimized for the terpolymerization. The structure and properties of the terpolymers were characterized by FTIR, 13C (1H) NMR, DSC and GPC. The optimum incorporation content of 11-chloro-1-undecylene within the terpolymer chains is up to 3.58 mol%. The polar monomers did not carry out the homopolymerization itself, but efficiently joined the terpolymerization with ethylene and propylene. Propylene monomer was in favor of the copolymerization with ethylene beside its homopolymerization. But polypropylene segments were not observed within the terpolymer chains. Compared to the polar monomers and propylene, ethylene was the most efficient monomer for joining the terpolymerization of ethylene/propylene/ω-Cl-α-vinyl monomers, and longer segments of polyethylene were produced within the terpolymer chains. M w up to 2×105 g/mol of the terpolymers was obtained by the catalyst system. The terpolymer molecular weight distribution (MWD) was about 2 to 3, implying the terpolymerization behavior followed the single-site mechanism.

Radical polymerization of styrene mediated by 9-(1-phenylethyl)-9-((1-phenylethyl)thio)-9 H -thioxanthene

Rapid progress in controlled/living radical polymerization (CLRP) has been achieved since the end of the last century. However, the demerits and limitations of existed methods impede their industrial applications on a large scale. Therefore, it is prominent to develop new CLRP methods that are better in controlled/living features, more simple, feasible and environmental-friendly. In this article, a new thioether, 9-(1-phenylethyl)-9-((1-phenylethyl)thio)-9 H -thioxanthene (DPETTX) was synthesized. Then, the polymerization behavior of St initiated by DPETTX and both DPETTX and a small amount of 2,2′-azobisisoheptonitrile (ABVN) was studied. Results show that DPETTX can initiated the polymerization of St at a high temperature ( 100 °C ) with low initiation efficiency, while St polymerization at a low temperature ( 55 °C ) was possible in the presence of a small amount of ABVN and number average molecular weight ( M n) increased continuously with increasing conversion of St. M n increased from 27 k to 46 k when a molar ratio of ABVN/DPETTX=0.05/1 was adopted. This co-initiating system based on DPETTX and a small amount of ABVN paves a new way for developing new CLRP methods.