Polymer structures can be roughly divided into two categories, i.e. single-chain
structure and their assembled structures. In the first category, single-chain
structures include the chemical structures and the conformations of polymer chains.
The chemical structures can be described at two separate levels, i.e. intrinsic and
extrinsic levels, corresponding to their roles in the determination of polymer
behaviors. The intrinsic factors are common for the same species of polymer
samples, including the chain semi-flexibility and the complicated inter-chain
interactions. The extrinsic factors are specific for the individual cases of polymer
samples, including molecular weights and their distributions, molecular topological
architectures, and the regularities of chemical sequences and their connections
along the chain. The conformation of polymer chains focuses on the variations of
chain conformation under various circumstances. In the second category, the
assembly structures of polymer chains show both static and dynamic aspects. For
the single-component homopolymer systems, the static structures include amor-
phous states, oriented states, liquid crystal states and crystalline states, whose
domains can interwoven into the texture of materials. For the polymer-based
multi-component systems, the above states can co-exist even in the mixed or
separated phases of solutions, blends, copolymers and composites. The dynamic
structures can be separated into crystalline and non-crystalline states. Most of the
crystalline states are formed by the semi-crystalline textures that appear as hard
elastomers. The non-crystalline states can be treated as glasses, rubbers or fluids
according to the different length scales of molecular mobility.
The physical properties of polymers vary with the structures hierarchical from
chemical structures to chain conformations and their assembly structures. The
mechanical properties are characterized by the impact strength, the tensile strength,
the bending strength and the hardness of polymers. The thermodynamic properties
are characterized by the heat resistance (physical aging, deformation temperature
and degradation temperature) and the solvent resistance of polymers. The responses
to photonic, electronic, magnetic, phonon and microwave stimulations are sepa-
rately characterized by the transparency, the conductivity, the dielectric constants,
etc. The transport properties of polymers have been applied to characterize the
filtration membranes for their efficiency of water purification, as well as the drag-
reduction agents to reduce the barrier for the enhanced oil recovery, for the long-
distance oil-piping and for the fire-extinction water-piping. The surface properties
of polymers are characterized by the friction, the adhesion and the electrostatics.
The chemical properties of polymers are characterized by the chemical aging,
degradation and cross-linking. Most of the above physical properties of polymers
have been well exploited and been widely applied in our daily life.
The current book is intended to be a concise introduction to polymer physics. As
such, it will mainly focus on polymer structures as well as their relationships with
properties (as elucidated by statistical thermodynamic and kinetic theories of
polymers), and may not be able to provide an extensive survey on polymer
properties and their wide applications. For a complementary knowledge about
polymer properties, the readers are directed to other textbooks of polymer physics
or specialized monographs about certain polymer properties.
8 1 Introduction