Ersin I. Serhatli

Synthesis of block copolymers by combination of photoinduced and atom transfer radical polymerization routes

Abstract Block copolymers of methyl methacrylate (MMA) and styrene (St) were obtained by the combination of two different free radical polymerization processes, namely photoinduced and atom transfer radical polymerization (ATRP) methods. In the first step, hydroxy terminated polymers were prepared by photoinitiated polymerization of MMA in the presence of N,N′-dimethylethanolamine and benzophenone as the initiating system and subsequently converted to bromine ended poly(methyl methacrylate) by the esterification of the resulting polymer with 2-bromo-propionylbromide. The functionalized polymers thus prepared were used as initiators in ATRP of St, in bulk, in conjunction with CuBr/2,2′-bipyridine as catalyst. The GPC and 1 H -NMR analysis, and the kinetic studies indicate a fully controlled/“living” radical polymerization which results in the formation of block copolymers with narrow polydispersities.

Chiral liquid-crystalline block copolymers based on polyether and mesogenic polyacrylate blocks

Abstract New liquid-crystalline ABA triblock copolymers containing crystalline polytetrahydrofuran (A) and chiral side-chain liquid-crystalline (B) blocks were prepared, and their phase behavior was studied. Block B was one of different polyacrylates containing the biphenyl mesogen variously spaced from the backbone and substituted with chiral groups, that are known to exhibit an electroclinic response in the chiral smectic A phase of the relevant homopolymers. The copolymers appeared to be phase-separated and formed mesophases characterized by lower transition temperature and enthalpy than those of the corresponding polyacrylate homopolymers.

Synthesis of liquid crystalline graft and block copolymers by sequential cationic and free-radical polymerizations

Abstraet-New graft and block copolymers were synthesized by two procedures, each consisting of a sequence of cationic and free-radical polymerization reactions. One polymer component was a liquid crystalline side-group polymer, with the other polymer component being incorporated in crystalline grafts or in amorphous blocks. The copolymers were microphase-separated and underwent thermal transitions (glass, melting, isotropization) of each individual component.

The mesophase structure of block copolymers with liquid crystalline and semicrystalline blocks

The mesophase structure of block copolymers containing liquid crystalline polyacrylate and semicrystalline poly(tetrahydrofuran) or poly(cyclohexene oxide) blocks was investigated by X-ray diffraction of powder samples. All the block copolymers were microphase separated, and the number and the nature of the mesophases (smectic E, B and A) were governed by the structure of the liquid crystalline block. We determined the lattice parameters of the mesophases and calculated the electron density profiles ρ(z) along the smectic layer normal.

Effect of acrylonitrile–butadiene–styrene/polyethylene terephthalate blends on dimensional stability, morphological, physical and mechanical properties and after aging at elevated temperature

A melt blending method was used to prepare acrylonitrile–butadiene–styrene terpolymer and polyethylene terephthalate blends to develop a new blend which can withstand higher temperatures required especially for automotive or home appliance paint curing processes. Blends were characterized by rheological, thermal and mechanical properties. Dimensional stability at 125°C was used to correlate with injection molded part shrinkage. The melt viscosity–composition curves for acrylonitrile–butadiene–styrene/polyethylene terephthalate blends exhibited a trend like the rule of mixtures in which adding acrylonitrile–butadiene–styrene to polyethylene terephthalate improved the processability. Scanning electron microscopy examination revealed different morphologies depending on the composition such as dispersed, co-continuous and phase inverted, which indicated that the binary blends were immiscible and form a two-phase structure. Tensile properties increased with an increase in the polyethylene terephthalate content while the unnotched impact strength reached a maximum at 40 wt.% acrylonitrile–butadiene–styrene content. In differential scanning calorimetry analysis, no partial miscibility was observed from the polyethylene terephthalate phase melting temperature shifts as compared to those of the neat component. Also, acrylonitrile–butadiene–styrene phases acted as nucleating agents due to change in polyethylene terephthalate cold crystallization temperature. In applied post shrinkage measurements by heat aging, we saw that the acrylonitrile–butadiene–styrene dimensional stability was improved with added polyethylene terephthalate.