从高分子的主要物理行为与分子结构之间已知的、内在的本质对应关系出发，初步勾勒出一个简单的包含高分子物理基础教学中所要求介绍的大多数基本概念的逻辑框架，即以两个共性特征和3个个性特征来描述高分子的基本结构，以便理顺高分子结构与性质之间的对应关系，在较短的时间内达到更好的教学效果。

We studied the athermal relaxation of bulk extended chains and the isothermal crystallization in an intermediately relaxed melt by means of dynamic Monte Carlo simulations of latticepolymer systems. The melt contained a memory of chain orientations but no more crystalline order. We found that the athermal relaxation is continuous and homogeneous among the bulk chains, and its rate depends on the chain length. The orientational memory in the melt significantly enhances the rate of rystallization. Nevertheless, no precursor of crystallization occurs in the melt of uniform chain lengths. But, in a binary blend of different chain lengths, the crystallization of oriented long chains acts as the precursor to induce epitaxial crystallization of the relaxed short chains. This mechanism explains the formation of shish-kebab crystals observed frequently in the processing of semicrystalline polymers. The results suggest that in flow-induced polymer crystallization the orientational relaxation of chains decides a selection of the long-chain component and then the precursor formation.

The morphological metastability of spontaneous crystallization from the melt of short-chain semiflexible homopolymers was studied through dynamic Monte Carlo simulations of a lattice multiple-chain system. Frictional hindrance for the sliding diffusion of the chains in the crystallites was employed to enhance the metastability of folded-chain crystallites, and distinguish the polymer crystallite from its mesophase, though their phase transitions have the similar driving forces. The integral folding of short chains in the crystallites and the constant linear crystal growth rate were identified with the actual polymers. In addition, the roughness of the local growth front accompanied with the occasional reversals and jumplike advancing was observed, which cannot be explained by current models. The crowding of the dangling ends on the fold surface seems to be the main reason for suppressing the lateral growth front, and the mechanism of chain folding was proposed. Its implications to the special behaviors of polymer melt crystallization, such as the semicrystalline state, the effect of the chain rigidity and molecular weight to crystal growth, the reversible premelting, and molecular segregation are briefly discussed.

Crystal nucleation is an activated process. In a supersaturated solution, small crystallites may dissolve again. Crystals can only be formed when a (rare) fluctuation leads to the formation of a crystallite with a size that exceeds a threshold. The probability to form such a "critical" crystal nucleus is determined by its excess free energy. For a simple molecular crystal, 1 the free energy change for forming a small crystallite from the liquid is approximately given by

We report a numerical study of crystallization and melting in bulk statistical homogeneous (random), homogeneous (slightly alternating), and heterogeneous (produced in a batch reaction) copolymers formed by crystallizable monomers and noncrystallizable comonomers. In our dynamic Monte Carlo simulations of lattice chains, the current model further assumes that the comonomers cannot move into crystalline regions by sliding diffusion of the chains. We find that both the overall composition and the statistical distribution of the monomers affect the phase-transition temperature, the resulting relative crystallinity, and the crystal morphology. However, the final absolute crystallinity of homogeneous copolymers seems insensitive to these parameters. Intramolecular segregation between monomers and comonomers is accompanied by crystallization, demonstrating the concept of sequence segregation or nanophase separation of statistical copolymers with assembling structures like in thermoplasticelastomers. Moreover, if crystallization of homogeneous copolymers has started but not yet completed on cooling, subsequent heating will show cold crystallization before melting, which can be attributed to insertion-mode lamellar growth. For heterogeneous copolymers, intermolecular segregation occurs on cooling before crystallization. On the basis of our observations, a pair of master melting and crystallization curves for the crystallinity of a statistical copolymer as a function of temperature are suggested to reflect the characteristic of the monomer-sequence-length distribution. This suggestion facilitates the clarification to the kinetic disturbance in local temperature regions and to the principle of some fractionation methods, such as temperature rising elution fractionation (TREF).