什么是聚合物的结晶_师谜登同学化学作业《什么是聚合物的结晶》归类分享_化学_师谜登
编辑： admin 2017-26-06
-
4
什么是聚合物的结晶导读：
学好数理化走遍天下都不怕，这说明化学很重要，那么同学们就要多多练习化学作业，我们就一起来看看师谜登同学的这道化学题，将给我们带来了哪些化学解题方法呢？什么是聚合物的结晶这道题主要考察的是化学基本知识，是师谜登精心归类总结的化学作业题——《什么是聚合物的结晶：什么是聚合物的结晶》，指导老师是武老师，涉及到的化学课本知识为：什么是聚合物的结晶，这道题的难度适中，考点为什么是聚合物的结晶：什么是聚合物的结晶的相关化学知识点，用所学的相关化学知识来进行解答，下面是师谜登化学作业的详细归类分享（本道题以问答模式展开）。
题目：什么是聚合物的结晶
什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
一般把相对分子质量高于10000的分子称为高分子.高分子通常由103～105个原子以共价键连接而成.由于高分子多是由小分子通过聚合反应而制得的,因此也常被称为聚合物或高聚物,用于聚合的小分子则被称为“单体”.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
能够发生聚合的低分子量化合物叫单体,它们的主要成分是碳和氢,在一定条件和催化剂作用下,单体聚合成以碳原子为骨架的长链,就叫聚合物.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
高分子化合物几乎无挥发性,常温下常以固态或液态存在.固态高聚物按其结构形态可分为晶态和非晶态.前者分子排列规整有序；而后者分子排列无规则.同一种高分子化合物可以兼具晶态和非晶态两种结构.大多数的合成树脂都是非晶态结构.其他同学给出的参考思路：
聚合物结成晶体互助这道作业题的同学还参与了下面的作业题
题1： 【聚合物结晶对性能会产生哪些影响?】[化学科目]
结晶可以使聚合物强度硬度增加,但结晶后分子链和链段规整排列到晶格中,运动困难,会使韧性下降易发生脆性断裂.同时由于晶区和非晶区的折射率不同,聚合物会变的不透明.题2： 【聚合物各种结晶形态的特征是什么】
分析结晶形态从一下几个方面 链的对称性 规整性 共聚 支化和交联对称性 越高越易结晶什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
规整性 对于主链中含有手性中心的聚合物 如果手性中心的构型完全是无规的 使高分子链的对称性和规则性都遭到破坏 这样的高分子一般不能结晶什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
如果两种共聚单元的共聚物有相同类型的结晶结构 那么共聚物也能结晶 分子间力也往往使链柔顺性降低 影响结晶能力 分子间能形成氢键 则利于结晶结构的稳定什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
从上面可以看出 可以影响聚合物的熔点 强度 等 特征会因此不同 大多按照上面分析 结晶形态 会随上述因素发生较大的变化 逐一分析题3： 聚合物成结晶区需要哪些条件?如何减少聚合物的结晶取向
聚合物结晶的影响因素可以分两部分：内部结构的规整性,以及外部的浓度、溶剂、温度等.结构越规整,越容易结晶,反之则越不容易,成为无定型聚合物.结构因素是最主要的.要减少聚合物的结晶取向,从结构来说,可以：减少分子链的对称性；减少分子链的立体规整性；降低重复单元的排列有序性,即无规共聚；减少分子链内含的氢键；提高分子链的支化度或交联度；从外部因素来看,可以：快速冷却,即淬火；什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
注意应力的影响.如橡胶,应力条件下就快速结晶.题4： 【天然橡胶是半结晶聚合物吗】
是的.题5： 请问：什么叫结晶?结晶聚合物是什么意思?
聚合物是通称一些非常长的分子,当中由结构单位和重覆单位经共价化学键连接一起. (英文Polymer起源自希腊语中polys即"许多",meros即部分). 聚合物与其它分子不同之处在於他们是由许多相同、相似或互补的亚单位重复所组成.这些亚单位或称单体是一些低至中等分子质量的分子,他们经聚合作用的化学反应便可组成聚合物.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
相似的单体由於有不同的取代基,所以不会是完全相同的.由不同的单体组成的聚合物会有不同的特性例如：溶解度、弹性和强度.譬如在蛋白质里、这些差异使聚合物能形成其独特的生物活跃构象(参见自我组装).当中相同单体如有非活泼的支链会导致聚合物链形成一无规线团——即根据数学模型所描述的理想链.虽然多数聚合物是有机化合物,并由碳基之单体所组成,但是也有无机聚合物例如,矽橡胶(又称硅树脂)是由交替的硅和氧原子所组成.目录 [隐藏]1 Polymer nomenclature 2 聚合物的物理性质 2.1 Branching 2.2 Stereoregularity 3 Constitution of polymers 3.1 Copolymers 4 Chemical properties of polymers 4.1 Intermolecular forces 4.2 Polymer characterization 5 See also 6 External links [编辑]Polymer nomenclaturePolymers are typically classified according to three main groups:thermoplastics (linear or branched chains) thermosets (crosslinked chains) elastomers Coordination polymers什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
The term polymer covers a large, diverse group of molecules, including substances from proteins to stiff, high-strength Kevlar fibres. For example, the formation of polyethene (also called polyethylene) involves thousands of ethene molecules bonded together to form a straight (or branched) chain of repeating -CH2-CH2- units (with a -CH3 at each terminal):什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Polymers are often named in terms of the monomer from which they are made. Because it is synthesized from ethene in a process during which all the double bonds in the vinyl monomers are lost, polyethene has the unsaturated structure:If it were named according to its final structure, it would have the alkane designation "polyethane".什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Because synthetic polymer formation is governed by random assembly from the constituent monomers, polymer chains within a solution or substance are generally not of equal length. This is unlike basic, smaller molecules in which every atom is stoichiometrically accounted for, and each molecule has a set molecular mass. An ensemble of differing chain lengths, often obeying a normal (Gaussian) distribution, occurs because polymer chains terminate during polymerization after random amounts of chain lengthening (propagation).什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Proteins are polymers of amino acids. Typically, hundreds of the (nominally) twenty different amino acid monomers make up a protein chain, and the sequence of monomers determines its shape and biological function. (There are also shorter oligopeptides which function as hormones.) But there are active regions, surrounded by, as is believed now (Aug 2003), structural regions, whose sole role is to expose the active regions. (There may be more than one on a given protein.) So the exact sequence of amino acids in certain parts of the chains can vary from species to species, and even given mutations within a species, so long as the active sites are properly accessible. Also, whereas the formation of polyethylene occurs spontaneously under the right conditions, the synthesis of biopolymers such as proteins and nucleic acids requires the help of enzyme catalysts, substances that facilitate and accelerate reactions. Unlike synthetic polymers, these biopolymers have exact sequences and lengths. (This does not include the carbohydrates.) Since the 1950s, catalysts have also revolutionised the development of synthetic polymers. By allowing more careful control over polymerization reactions, polymers with new properties, such as the ability to emit coloured light, have been manufactured.[编辑]聚合物的物理性质聚合物的物理性质包括聚合度,分子量分布,结晶度和相转变等,详见高分子物理学.[编辑]BranchingSee also: Branching (chemistry)什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
During the propagation of polymer chains, branching can occur. In free-radical polymerization, this occurs when a chain curls back and bonds to an earlier part of the chain. When this curl breaks, it leaves small chains sprouting from the main carbon backbone. Branched carbon chains cannot line up as close to each other as unbranched chains can. This causes less contact between atoms of different chains, and fewer opportunities for induced or permanent dipoles to occur. A low density results from the chains being further apart. Lower melting points and tensile strengths are evident, because the intermolecular bonds are weaker and require less energy to break.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Besides branching, polymers can have other topologies: linear, network (cross-linked 3D structure), IPN (integrated polymer network), comb, or star as well as dendrimer and hyperbranched structures.[编辑]Stereoregularity什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Stereoregularity or tacticity describes the isomeric arrangement of functional groups on the backbone of carbon chains. Isotactic chains are defined as having substituent groups aligned in one direction. This enables them to line up close to each other, creating crystalline areas and resulting in highly rigid polymers.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
In contrast, atactic chains have randomly aligned substituent groups. The chains do not fit together well and the intermolecular forces are low. This leads to a low density and tensile strength, but a high degree of flexibility.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Syndiotactic substituent groups alternate regularly in opposite directions. Because of this regularity, syndiotactic chains can position themselves close to each other, though not as close as isotactic polymers. Syndiotactic polymers have better impact strength than isotactic polymers because of the higher flexibility resulting from their weaker intermolecular forces.[编辑]Constitution of polymers[编辑]Copolymers什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Copolymerization with two or more different monomers results in chains with varied properties. There are twenty amino acid monomers whose sequence results in different shapes and functions of protein chains. Copolymerising ethene with small amounts of 1-hexene (or 4-methyl-1-pentene) is one way to form linear low-density polyethene (LLDPE). (See polyethylene.) The C4 branches resulting from the hexene lower the density and prevent large crystalline regions from forming within the polymer, as they do in HDPE. This means that LLDPE can withstand strong tearing forces while maintaining flexibility.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
A block copolymer is formed when the reaction is carried out in a stepwise manner, leading to a structure with long sequences or blocks of one monomer alternating with long sequences of the other. There are also graft copolymers, in which entire chains of one kind (e.g., polystyrene) are made to grow out of the sides of chains of another kind (e.g., polybutadiene), resulting in a product that is less brittle and more impact-resistant. Thus, block and graft copolymers can combine the useful properties of both constituents and often behave as quasi-two-phase systems.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
The following is an example of step-growth polymerization, or condensation polymerization, in which a molecule of water is given off and nylon is formed. The properties of the nylon are determined by the R and R' groups in the monomers used.Image:Con polymer.png什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
The first commercially successful, completely synthetic polymer was nylon 6,6, with alkane chains R = 4C (adipic acid) and R' = 6C (hexamethylene diamine). Including the two carboxyl carbons, each monomer donates 6 carbons; hence the name. In naming nylons, the number of carbons from the diamine is given first and the number from the diacid second. Kevlar is an aromatic nylon in which both R and R' are benzene rings.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Copolymers illustrate the point that the repeating unit in a polymer, such as a nylon, polyester or polyurethane, is often made up of two (or more) monomers.[编辑]Chemical properties of polymers[编辑]Intermolecular forces什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
The attractive forces between polymer chains play a large part in determining a polymer's properties. Because polymer chains are so long, these interchain forces are amplified far beyond the attractions between conventional molecules. Also, longer chains are more amorphous (randomly oriented). Polymers can be visualised as tangled spaghetti chains - pulling any one spaghetti strand out is a lot harder the more tangled the chains are. These stronger forces typically result in high tensile strength and melting points.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
The intermolecular forces in polymers are determined by dipoles in the monomer units. Polymers containing amide groups can form hydrogen bonds between adjacent chains; the positive hydrogen atoms in N-H groups of one chain are strongly attracted to the oxygen atoms in C=O groups on another. These strong hydrogen bonds result in, for example, the high tensile strength and melting point of kevlar. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so ethene's melting point and strength are lower than Kevlar's, but polyesters have greater flexibility.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
Ethene, however, has no permanent dipole. The attractive forces between polyethene chains arise from weak van der Waals forces. Molecules can be thought of as being surrounded by a cloud of negative electrons. As two polymer chains approach, their electron clouds repel one another. This has the effect of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side. This charge is enough to actually attract the second polymer chain. Van der Waals forces are quite weak, however, so polyethene melts at low temperatures.[编辑]Polymer characterization什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
The characterization of a polymer requires several parameters which need to be specified. This is because a polymer actually consists of a statistical distribution of chains of varying lengths, and each chain consists of monomer residues which affect its properties.什么是聚合物的结晶：逆火学习站的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
A variety of lab techniques are used to determine the properties of polymers. Techniques such as wide angle X-ray scattering, small angle X-ray scattering, and small angle neutron scattering are used to determine the crystalline structure of polymers. Gel permeation chromatography is used to determine the number average molecular weight, weight average molecular weight, and polydispersity. FTIR is used to determine composition. Thermal properties such as the glass transition temperature and melting point can be determined by differential scanning calorimetry and dynamic mechanical analysis. Pyrolysis followed by analysis of the fragments is one more technique for determining the possible structure of the polymer.什么是聚合物的结晶：逆火学习站(img1.72589.com)的师谜登同学的作业题：《什么是聚合物的结晶》解题思路
什么是聚合物的结晶小结：
通过以上关于师谜登同学对什么是聚合物的结晶：什么是聚合物的结晶的解题归类详细分享，相信同学们已经对什么是聚合物的结晶的相关化学作业考点一定有所收获吧。建议同学们要学会归类总结，并仔细思考师谜登同学分享的解答《什么是聚合物的结晶》这道作业题的解题思路，把化学考试中可能涵盖的考点都在平时得到加强训练，才能让自己的化学考试获得好成绩。