1.1 Determination of the molecular weight of the polymer by the viscosity method The greatest feature of the polymer is its large molecular size and high molecular weight. The determination of the molecular weight of polymers is the most basic experimental technique of polymer physics. Many methods for measuring the molecular weight of polymers are available, such as lower freezing point, higher boiling point end group titration, osmotic pressure, light scattering, GPC, etc., among which the viscosity of capillary viscometer is used as a tool. The method is the simplest and most practical. By measuring the viscosity, students can understand the statistical mean of the molecular weight of the polymer.
1.2 Molecular weight of the fractionated polymer The polydispersity is another characteristic of the polymer. Therefore, the determination of the molecular weight distribution should be one of the basic experiments of polymer physics. Although automated instruments such as GPC are now available, the solubility grading method based on the solubility dependence of the polymer molecular weight remains the classical experimental method. The training of students' hands-on ability in macromolecular solution is particularly helpful and is also a necessary means for preparing macroscopically-dispersed samples. 1.3 Swelling High elasticity is a characteristic property of polymers, and rubber is a very special polymer material. The establishment of polymer science has a special role. As a cross-linked polymer, the rubber does not dissolve in the solvent and only swells, which is one of the characteristics of the polymer. Swelling experiments were conducted using the volumetric method, the apparatus was simple, and the polymer solution theory and high elasticity theory were able to be contacted.
1.4 Glass Transition Glass Transition, although not specific to the polymer, but in the general experimental conditions (at room temperature up and down several tens of degrees and general strain rate) the polymer shows a clear glass transition phenomenon measured glass transition is the most classic The experiment is to determine the specific volume temperature curve of cnki by the bulk dilatometer method. Extrapolating the intersection point from the straight line parts at both ends of the curve is the glass transition temperature Tg specific volume temperature curve which is most easily explained by the free volume theory and is therefore the most basic high. Molecular physics experiments have different Tg values ​​due to different heating (or cooling) rates (this is experimentally very easy to do) and are very helpful in understanding the relaxation phenomena that exist in polymers. The body dilatometer experiment is simple and is a useful experiment that cannot be abandoned. The deformation temperature curve is also the most common polymer experiment. It not only reflects the three mechanical states of the polymer, but also determines the Tg viscosity temperature Tf of the amorphous polymer and the melting temperature Tm of the crystalline polymer, thereby estimating the tested sample. The use of temperature, it can also understand the dynamic nature of the glass transition temperature 1.5 corrugated silver is a special phenomenon in the polymer fracture, and cracks, the silver is not empty, and there are more than 50% of the polymerization Things. Therefore, the corrugation experiment includes solvent fracturing. It can not only understand the yield and fracture of the polymer, but also understand the environmental stability of the polymer fracture. The silver streaking experimental device is also very simple and can be manufactured entirely by itself.
1.6 Observation of spherulites Spherulitic crystals are a special form of polymer crystals. Due to the extreme asymmetry of macromolecules, the crystalline state of polymers is poorer than that of small molecules, whereas the order of amorphous states is smaller than that of small molecules. It's good. By observing the polymer spherulites, not only can the characteristics of the polymer be understood, but also a practical method of observing the crystal morphology of the polymer by using an optical microscope or a small-angle laser light scattering device can be learned.
This is also the case with the computer-driven polymer chain rotation and flexibility mentioned below.
2 Polymer physics experiments should be based on the principle of do-it-yourself collocation. Given the prevailing under-funded situation in universities, macromolecule physics experiment class should try its best to save the consumption of solvents and materials and create experimental devices by themselves. In the molecular weight experiment, polyvinyl alcohol can be used as a polymer sample, so that the solvent is the cheapest water. Currently, there is almost no experimental equipment for the production of polymer physics teaching. It is not allowed to purchase equipment for scientific research for teaching experiments. of. Therefore, it is necessary to make a simple equipment like the deformation temperature curve of a polymer, which can be used to make a teaching experiment. The differential transformer can be used to measure the deformation, the regulator transformer can control the constant heating, and the wide mouth Dewar flask can be used as a special deformation temperature curve for the thermal insulation jacket. The measuring device is very effective, durable and not easily damaged. In another example, the silver vein tester stretches a polystyrene (PS) strip using a simplest screw stretching device (by cutting it out with a tape cartridge) and measures the stress with a commercial spring balance. In particular, self-made experimental devices can require students to personally combine and connect cables, which greatly enhances students' enthusiasm for experimentation. 3 Polymer physics experiment teaching should promptly reflect the research results of polymer physics. We researched the development of thermosetting resins and resin-based composites. The dynamic torsional vibration method of the material reflects the cross-linking reaction by the change of the mechanical quantity when the resin is cured, monitors the whole process of the resin from the liquid to the solid state transition, simulates the entire molding process realistically, and reflects the law of the mechanical properties of the resin changing with the temperature. Some parameters of the apparent kinetics of the curing reaction use the resin-curing instrument to teach student experiments. It is very innovative to determine the gelation time and the apparent activation energy of the epoxy resin. 4 To introduce the computer technology into the polymer physics experiment as much as possible. In recent years, computer-aided methods that can simulate the structure and behavior of real development systems have formed a whole new field. This is called "molecular simulation." With the rapid development of computer technology, there is a large amount of computer software for high Chain Structure, Condensed Structure, Monte Carlo Module in Molecular Science Polymer materials and design, but no one has yet reported polymer useful in computer software open teaching experiment. We believe that computer experiments in polymer teaching will undoubtedly have unique features in terms of intuitive xnki and interest. We use the “nature of molecules†developed by the Institute of Chemistry, Chinese Academy of Sciences (abbreviation). MP) software sets up two experiments: constructing isotactic polypropylene molecules with "molecular properties" software, and calculating the linear distances of their ends and calculating the poly(methyl acrylate) using the “molecular nature†software. Conformational energy involves orientational polymerization, internal rotation of polymer chains, internal rotation energy, flexibility, terminal distance, and other knowledge points. MP uses computers to simulate the structure and behavior of molecules at the molecular level of atoms, thereby mimicking various physical and molecular systems. Chemical properties. Molecular simulation methods can not only simulate the static structure of molecules, but also simulate the dynamic behavior of molecules (such as the bending motion of molecular chains, the association and disassociation of intermolecular hydrogen bonds, the adsorption behavior of molecules on the surface, and the diffusion of molecules). This method enables general experiment chemists and experimental physicists to conveniently use the molecular simulation method to see the movement of molecules on the screen. It is as realistic as the movie. The above two experiments have been set up since 1996. Students reflect the results on the screen. The rotation of the macromolecular chains and three-dimensional space has the effect of using physical molecular models that were previously unattainable. At the same time, students have a great interest in experimentation and contend to operate on computers themselves. Since computers and software are available for such experiments, usually Almost no maintenance fees are required, which is very beneficial to experimental teaching. Of course, those experimental techniques that are not commonly used in the society today must be determined to be deleted from the teaching experiment.