1.1 Addition polymerization (แบบการเติม) Classification(3): polymerization methods Addition-Condensation system 1.1 Addition polymerization (แบบการเติม) 1.2 Condensation polymerization (แบบควบแน่น) Chain growth-Step Growth System 2.1 Chain growth polymerization (แบบลูกโซ่) 2.2 Step growth polymerization (แบบขั้น)

1.2 Condensation polymerization (แบบควบแน่น) 1. Addition-Condensation system 1.1 Addition polymerization (แบบการเติม) Monomer molecules become part of the polymer without kicking any molecules out. 1.2 Condensation polymerization (แบบควบแน่น) Part of the monomer molecule is kicked out when the monomer becomes part pf the polymer. The part that gets kicked out is usually a small molecule like water (H2O), or HCl gas

2. Chain Growth-Step Growth System 2.1 Chain growth polymerization (แบบลูกโซ่) monomers become part of the polymer one at a time.

2.2 Step growth polymerization (แบบขั้น) or monomer + monomer = dimer dimer + monomer = trimer dimer + dimer = tetramer trimer + dimer = pentamer n-mer + m-mer = (n+m)mer Two short chains can react to form longer chain

Chain-Growth (or addition) polymerization

Example: H H C = C C C n n monomer polymer n Polyethylene Ethylene When ethylene is polymerized to make polyethylene, the every atom of the ethylene molecule becomes part of the polymer (none gained, none lost) Polymer Technology (A. Cattaleeya)

In General; Addition Polymerization = Chain Growth Polymerization - do not give off by product - monomers become part of the polymer one at a time ประกอบด้วยขั้นตอนต่างๆ 3 ขั้นตอน และมีการใช้สารเคมี 2 ชนิด 1. initiation ขั้นเริ่มต้นปฏิกิริยา 1. monomer 2. Prapagation ขั้นดำเนินไปของปฏิกิริยา 2. initiator 3. termination ขั้นสิ้นสุดปฏิกิริยา Free radical Anionic - Cationic +

Monomer Initiator Becomes repeating units in polymer chains Functions of the 2 basic chemicals Monomer Becomes repeating units in polymer chains Monomer need to have at least 1double bond Initiator - add into monomer to activate joining of monomers into long polymer chains

There are 3 types of chain growth polymerizations: Free radical polymerization (Free radical initiator I) Anionic polymerization (Anionic initiator I-) Cationic polymerisation (Cationic initiator I+) (names depend on type of initiator)

Free radical polymerization Initiator peroxide (ROOR, HOOH) Azo compound (-N=N-) easily decompose into 2 free radicals when exposed to heat H3C – C – N = N – C - CH3 CH3 CN H3C – C CH3 CN C - CH3 CH3 CN + N N + O O O C – O O - C C – O – O - C + O O C C – O +

1. Initiation step C = C H C C H Free radical จะกระตุ้นให้พันธะคู่ในโมโนเมอร์แตกออก แล้วเกิดพันธะใหม่ขึ้น

2. Propagation Step C C H C = C H C C H C C H n Free radical ที่ปลายจะไปกระตุ้น monomer ตัวที่อยู่ใกล้คียงให้พันธะคู่แตกออก Monomer ตัวที่เหลือจะเข้าต่อที่ปลายในลักษณะเดียวกันไปเรื่อยๆ

3. ขั้นสิ้นสุดปฏิกิริยา (Termination step) ขั้นการสิ้นสุดของปฏิกิริยา มี 3 แบบ : 1. Coupling: Mx + My Mx+y 2. Disproportionation: Mx + My Mx + My-1 3. Chain transfer agent: -C = C H H C – Cl H C H + Cl – C – Cl Cl Cl + Cl – C Cl Initiate another chain

Anionic polymerization (I-) Initiator CH3 – CH2 – CH2 – CH2 - Li butyl lithium H CH3 – CH2 – CH2 – CH2 - Li - Li + CH3 – CH2 – CH2 – C + H

1.ขั้นเริ่มต้นปฏิกิริยา (Initiation step I-) H C = C H - Li + CH3 – CH2 – CH2 – C H H - Li + CH3 – CH2 – CH2 – CH2 - C H

2. ขั้นดำเนินไปของปฏิกิริยา (Propagation Step II.) H C = C H - Li + CH3 – CH2 – CH2 – CH2 - C + H H H H C C H n - - Li + CH3 – CH2 – CH2 – CH2 - C – C – C H H H

Living anionic polymerization butadiene Living polystyrene Here A stands for the initiator fragment end groups. Sometimes it’s a butyl group from butyl lithium, sometimes it isn’t. Living styrene-butadiene block copolymer - A – A – A – A – A – A – A – A – B – B – B – B – B – B – B - B Block copolymer

Cationic polymerisation (I+)

1.ขั้นเริ่มต้นปฏิกิริยา (Initiation step I+) Initiator: AlCl3/H2O - + + AlCl3/H2O

2. ขั้นดำเนินไปของปฏิกิริยา (Propagation Step)

Step-Growth (Condensation) Polymerization

In General; Condensation Polymerization = Step Growth Polymerization - give off by product - monomers become part of the polymer one at a time or two short chain react to form longer chain

เอสเทอร์ริฟิเคชัน (esterification) H + H2O acid alcohol ester

monomer ที่ใช้ต้องมีหมู่ฟังก์ชันอย่างน้อย 2 หมู่ diacid dial polyester

PET +n H2O Polymer Technology (A. Cattaleeya)

The first thing the two monomers will react to form a dimer. Terapheyl chloride Ethylene glycol ester dimer

2-mer + 2-mer = 4-mer monomer + monomer = 2-mer + HCl monomer + monomer = 2-mer 2-mer + monomer = 3-mer 2-mer + 2-mer = 4-mer 3-mer + dimer = 5-mer n-mer + m-mer = (n+m)mer

Nylon 6,6 nylon 6,6 adipoyl chloride hexamethylene diamine + N-CH2-CH2-CH2-CH2-CH2-CH2-N H Cl-C-CH2-CH2-CH2-CH2-C-Cl O This Cl atom and this H atom don’t end up in the polymer, they split off to form HCl gas. HCl + C-CH2-CH2-CH2-CH2-C- O N-CH2-CH2-CH2-CH2-CH2-CH2-N H n nylon 6,6

In a condensation polymerization, some atoms of the monomer don’t end up in the polymer. + N-CH2-CH2-CH2-CH2-CH2-CH2-N H Cl-C-CH2-CH2-CH2-CH2-C-Cl O HCl + C-CH2-CH2-CH2-CH2-C- O N-CH2-CH2-CH2-CH2-CH2-CH2-N H n When nylon 6,6 is made from adipoyl chloride and hexamethylene diamine, the chlorine atoms from the adipoyl chloride, each along with one of the amine hydrogen atoms, are expelled in the form of HCl gas.

One example is the polymerization which produces polyurethane One example is the polymerization which produces polyurethane. There are also addition polymerization which are step growth polymerizations. Isocyanate groups a diisocyanate a diol Not only monomers react, but also dimers, trimer, and so on. This makes it a step growth polymerization. Also, because no small molecule by-products are produced, it is an addition polymerization. เอกสารประกอบจาก ดร.ธนาวดี ลี้จากภัย MTEC

Conclusion Chain growth polymerization: generally = addition polymerization : monomer become part of the polymer one at a time. Polymer chain grows rapidly to a long size as soon as the initiation step starts. High molecular weight polymer is formed immediately. monomer concentration decreases as the number of high polymer molecules increase the reaction mixture contains-monomer, high-molecular weight polymer, growing chain

Conclusion Step growth polymerization: generally = condensation polymerization : Two short chains can react to form longer chain. monomer disappears much faster molecular weight increase through out the course of the reaction high molecular weight polymer is not obtained until the end of the reaction

Ref: S.L. Rosen, John Wiley & Sons 1993

Classification(4): Architecture of Chain Each structures respond to solvents differently. Linear and Branched Polymers – can be soluble in suitable solvents LDPE LLDPE HDPE Linear polymers Branched polymers

Crosslink polymers Heavily crosslinked  not soluble and not swell ex. Ebonite bowling ball – no swelling Lightly crosslinked  not soluble but swell in solvent

Classification(5): Number of repeating unit present in the polymer chains homopolymer (PE, PP, PS, PVC, PMMA, PC, PET), copolymer (SBR, NBR), terpolymer (ABS)

Alternating copolymer Different types of copolymers —xxoooxoxooxxxox— Random copolymer —xoxoxoxoxoxoxo— Alternating copolymer —xxxxxooooooxxxx— Block copolymer Graft copolymer

โคโพลิเมอร์ที่มีคาร์บอนเป็นโครงสร้างหลัก (Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)

(Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)

Classification(6): orientation of polymer chains (Morphology) Amorphous Semi-crystalline

Polymer Thermoplastic Elastomer Thermoset Semi-Crystalline Amorphous ( lightly cross linked) (heavily cross linked ) Network Cross linked polymers Linear/branched polymers (no cross linked)

T Viscous melt Tm Leathery Tg Brittle % crystallinity ~70% rubbery ductile Tg Brittle Hard&Strong % crystallinity ~70%

Influence of molecular weight on properties of polymers ( Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)

Chapter 4: Orientations and Crystallinity of Polymers

Orientation of Polymer Chains Connection of chain (Configurational features) - Geometric details of how each repeat unit adds to the growing chain - Occur during polymerization process (cannot change by rotation) Rotation and twisting of chain (Conformation) - rotation of backbone or side group

Factors affecting Crystallinity of Polymers Factors that affect properties of polymers Architectural features MW and MWD Configurational features Stereoregularity (conformation) Architectural features: Branching Cross linking Nature of copolymer

2. Molecular weight (MW), Molecular Weight Distribution (MWD): Polymers with long chain and narrow molecular weigth distribution  more crystallinity High MW Low MWD Easily crystallized

“Head to Head”/“Tail to Tail” Configurations: Geometric details of how each repeat unit adds to the growing chain affect properties of polymers - Head to Head - Head to Tail (normal arrangement) - Tail to Tail “Head to tail” “Head to Head”/“Tail to Tail” Configuration: cannot be changed by rotation of the backbone.

4. Stereoregularity—rotation around the backbone (rotation of backbone or side groups) - Rotation of backbone Rotation of Cn-Cn+1 bond Gauche positive (g+) Trans (t) [lowest potential energy—most probable] Gauche negative (g-) Cis-Tran Isomer for C=C Trans conformation: all backbones lie in the same plane-planar zigzag plane - Rotation of side group - isotactic - syndiotactic - atactic (Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)

potential energy of each Rotation of Cn-Cn+1 bond Gauche positive (g+) Trans (t) Gauche negative (g-) potential energy of each conformation Trans conformation (Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)

Cis-Trans Isomer (Rotation of Cn=Cn+1 bond) Poly (cis-1,4-isoprene) Poly (trans-1,4-isoprene)

Rotation of side groups (Stereoisomerism) Ex. Repeat unit.

Ref.: L.H. Sperling, John Wiley & Sons, Inc. (1992)

Requirement for crystallinity Need ordered regular chain structure (syndiotactic+isotactic) The 2nd forces holding chains > disorder effect of thermal energy “Anything that reduces the regularity of backbone reduces the crystallinity.” Ex. PE, PP are crystalline polymers copolymer of PP/PE is amorphous “There is no complete crystalline polymers” % crystallinity – show fraction of crystal structure inside polymers

1. The Fringed Micelle Model Models for Crystal Formation 1. The Fringed Micelle Model 2. Folded-Chain model

3. Folded-Chain model Tie molecules

Crystal Growth Ref.: L.H. Sperling, John Wiley & Sons, Inc. (1992)

Steps of Spherulite Formation Ref.: L.H. Sperling, John Wiley & Sons, Inc. (1992)

Spherulite (cont.) Ref: R.J. Young and P.A. Lovell, Chapman&Hall 1991

Spherulites Spherulites grow radially from a point of nucleation until other spherulites are encountered.

XRD patterns of Amorphous and Semi-crystalline Polymers Ref: R.J. Young and P.A. Lovell, Chapman&Hall 1991

Spherulite (cont.) Size: size of spherulites can be controlled by the number of nuclei present. (normally dia. ~ 0.01 mm) No. Nucleation site Size of spherulites How to enhance transparency and reduce brittleness? Add nucleating agents Quench polymers (increases nucleation sites) or

Effect of Crystallinity on Mechanical Properties more crystallites   Ex: (density) > > branching < < % crystalline > > Degree of crystallinity: สมการ amorphous + crystalline Branching: more branching  less crystallinity HDPE LLDPE LDPE

Tacticity  crystallinity optical properties Atactic -->mostlyAmorphous polymers  transparent Isotactic mostly crystalline polymers Syndiotactic /refractive index of phase amorphous = phase crystalline transparent Size of crystallites < wavelength of visible light transparent Low degree of crystallinity  fairly transparent Ex1: Foam ex. Foamed PS  เป็นสีขาวทึบเพราะแสงผ่านเฟส PS และgas bubbles Ex2: high-impact PS  เป็น PS ที่มีอนุภาค polybutadiene rubber ขนาด 1-10 m. กระจายอยู่ใน amorphous PS

Effect of crystallinity on optical properties Basic concept: เมื่อขนาดของอีกเฟสหนึ่งมีขนาดใหญ่กว่า light passes btw. two phases ความยาวคลื่นของแสงเกิดการหักเหทึบแสง w/ different refractive indices เมื่อขนาดของอีกเฟสหนึ่งมีขนาดเล็กกว่า ความยาวคลื่นของแสงไม่เกิดการหักเหโปร่งแสง Light scatters. Light Passes through

Liquid Crystalline Polymers Molecules that show a degree of order in the liq. Phase If liq. Phase is solution  lyotropic LCP If liq. Phase is melt  thermotropic LCP is self reinforced composite Ex. (lyotropic) Kevlar เป็น aromatic polyamid (“aramid”) with repeating unit pull into fibers in the solution of H2SO4 use for bullet-proof vests (เสื้อเกราะกันกระสุน)

Ex. (thermotropic LCP) Vectra Xydar Note: liq. Crystalline polymers have highly aromatic backbone inhibit rotationstiff, rigid extended chain Xydar Vectra

Extended chain crystal When pulled polymer will align in the flow direction crystallize (extended chain crystal) (the more you pull, the stronger it becomes)

Stretching Curve and Crystal Orientation

Crystal Orientation with Stretching

XRD ring with Stretching