Chapter 2. Typology of Polymers

Transcription

1 Chpter 2. Typology of Polymers 2.1 Types of bonds in Polymers 1. primry ovlent nd metlli bonds 2. hydrogen bonding 3. dipole intertion 2nd fore 4. dispersion fore (vn der Wls fore) 5. ioni bond e.g.) polyproltone, (C 2 ) 5 C O + misible polymer blends C 2 C n PVC, Cl O n 2.2 Stereoisomerism Polymer onfigurtion rrngements of toms whih nnot be ltered exept by breking nd reforming primry hemil bonds. Configurtion in vinyl polymers i) Atti rndom rrngement of the unsymmetril group. [(e.g.) polypropylene oxide] C 3 O C C O C C O C C O C C C 3 C 3 C 3

2 ii) Isotti the struture in whih ll of the groups re lined up on the sme side of the bkbone. e.g.) PPO, i-pp (T m = 176 o C). O C C O C C O C C O C C C 3 C 3 C 3 C 3 iii)syndiotti lterting plement of the group on either side of the hin. C 3 C 3 O C C O C C O C C O C C C 3 C 3 Configurtion- speifies the reltive sptil rrngement of bonds in moleule (of given onstitution) without regrd to the hnges in moleulr shpe whih n rise beuse of rottions bout single bonds. A hnge in onfigurtion reguires the breking nd reforming of hemil bonds. Conformtion- the onformtion of mromoleule of given onstitution nd onfigurtion speifies the sptil rrngements of the vrious toms in the moleule tht my our beuse of rottions bout single

3 bonds. - vinyl polymer에서는 stereoregulrity가증가할수록 rystllinity가증가함. - no onfigurtionl isomers in PE Polymer onformtion- hnges in struture used by rottion bout single bond. - stereoisomerism in diene polymer ex) polybutdiene, i) is-pbd : the substituent groups on the double-sided rbons my either be on the sme side. C C = C C C C =C C n ii) trns-pbd : the substituent groups on the double-sided rbons my either be on the opposite side. C C = C C C C =C C n

4 1.3 Crystllinity 1. Reguirements for rystllinity Regulr hin struture. ex) iso-pp, iso-ps ydrogen bonding Strong dipole intertion. ex) nylon-6 2. The Fringed-Mielle Model solid stte polymer의분류 i) ompletely morphous ii) prtilly rystlline iii) lmost ompletely rystlline. Crystlline region rystllite(fringed-mielle) morphous region -severl hundred Å If they re strethed inrese rystllinity. - rystllites tie the individul hins together - the rystllites will generlly melt before the polymer degrdes 3. Folded-hin Crystllites - the growth of single rystls from dilute solution

5 i) regulr reentry model ii) djent reentry model iii) irregulr or swithbord reestry model - 두께는분자량에무관하고온도가증가할수록두께는증가하고 growth rte 가감소할수록 more perfet rystl 이얻어진다. - Chin folding why? 1000 Å 의길이가 100 Å 두께에들어갈려면 folding이일어나야한다. - Solution stte : lmelle (plte like polymer rystl) - Melt stte : model ombining the folded-hin lmelle with the interlmellr morphous mteril. 4. Extended-hin rystls. fibrillr struture polymers rystllized from melt while subjeted to extensionl flow ( eztended hin rystls) 5. spherulties ( 구정 ). polyrystl이란개념이며 single rystl 이아니다. spherulites re ggregtes of lmellr rystllites. 특징 ) i) grow rdilly from point of nuletion. ii)nulei가많으면작은 sphrulite 가많이생긴다. Shok ooling

6 smller spherulites. iii) 크기는약 0.01mm(dimeter) - Mltese Cross 구조관찰 iv)semirystlline polymer 에서볼수있는특징. 편광현미경으로 6. The effets of rystllinity on polymer properties LDPE (low density polyethylene) - long brnhed brnhes : mde by high-pressure proess.( 25,000-50,000 psi) δ=0.915g/m % rystllinity Tm= C LLDPE (liner low density polyethylene) - short, stright brnh : low-pressure (100 psi) Tm= C 54-63% rystllinity DPE (high density PE) - no brnhes, liner : mde by low pressure proess δ=0.97 g/m % rystllinity - more tightly pked in the rystlline thn in the morphous res. e.g.) iso-pp: rystlline, hrd nd rigid plstis. rystlline polymers hve two-phse systems with rystlline phse dispersed in n morphous mtrix- mostly opgue. In generl, trnsprent polymers re ompletely morphous. 7. Determintion of Crystllinity i) density mesurement ρ ρ φc = ρ ρ ρ : density of the smple ρ : density of morphous polymer ρ : density of rystlline polymer X-ry 의 unit ell dimension.

7 ω ρ = ρ ( ρ ρ ) ( ρ ρ ) ii) Speifi het (l/g ) χ = iii) melting enthlpy (enthlpy of fusion) χ = f iv) IR ε χ = ε λ λ e.g.)p.e : 7.67µm 에서 morphous. v) NMR Brod bnd : rystlline regions Shrp bnd : morphous regions vi) X-ry χ = I I + I I= integrting the intensities of rystlline refletions.

8 8. Rte of rystlliztion rte of rystlliztion temp. - rte of rystlliztion is mximum between Tg nd Tm of the polymer.. Seondry rystlliztion quenhing of speimen t melt temperture nd then store t temp. higher thn Tg the disordered regions will mobile enough to rerrngement into lower energy, more ordered struture.