Syndiotactic polystyrene physical properties

The physical and mechanical properties of a polymeric material critically depend on many factors, one of which is stereochemistry. Polymers that have chiral centers in the repeated unit can exhibit two structures of maximum order, isotactic and syndiotactic [27]. Sequential stereocenters of isotactic polymers are of same relative stereochemistry whereas those of syndiotactic polymers are of opposite relative configuration. Due to their stereoregularity, isotactic and syndiotactic polymers are typically crystalline, which is an important feature for many applications. Isotactic polymers are used in a wide range of applications. Typical examples include isotactic polyolefins and almost all natural polymers. In contrast, syndiotactic polymers have limited applications mainly due to their hard productivity and inherently alternating stereochemistry. The properties of syndiotactic polymers are usually similar to or in some cases better than isotactic counterparts according to the studies on syndiotactic polystyrene and other syndiotactic polyolefins [28]. Syndiotactic PLA is expected to be a versatile polymer with controllable stereochemistry. 

Recyclable blends of syndiotactic polystyrene, sPS, were prepared by blending sPS with a copolymer of styrene with either maleic anhydride (MA), or with glycidyl methaciylate (GMA), and with an elastomer, e.g., SEES, SBS, SBR, EPDM. The compositions showed good impact resistance, elongation and retention of physical properties upon... 

Several exciting new material based on co-crystalline and nanoporous crystalline phases of syndiotactic polystyrene have been achieved. In particular, several kinds of polymer co-crystalline phases have been prepared, belonging to three different classes 8- and e-clathrates and intercalates. Polymer cocrystals with active guest molecules show unusual physical properties, hence are promising for several kinds of advanced materials. Moreover, the unprecedented achievement of polymeric nanoporous crystalline phases (8 and e) has given very interesting results in the fields of molecular separations, water/ air purification and sensorics. 

Turek, D. A. Sununary of the physical properties of continuous melt-spun fibers formed from syndiotactic polystyrene and syndiotactic copolymers of styrene and paramethylstyrene. Dow Internal Report, September 1994. 

Isotactic and syndiotactic polymers can crystallize, while atactic polymers cannot. Polymers other than polypropylene that have tacticity include polystyrene, polyfvinyl chloride), and poly(methyl methacrylate). Thus there are crystalline and non-crystalline forms of these polymers. By use of a copolymer, the number of side groups, and thus the crystallinity can be precisely controlled. An important example is the copolymerization of ethylene and a higher alpha-olefin, such as butene or octane, to make linear low-density polyethylene (LLDPE), in which the crystallinity is governed by the fraction of comonomer incorporated into the chain. Tacticity can affect important physical properties such as the intrinsic viscosity and thus must be taken into accoimt in characterization methods such as gel permeation chromatography. 

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